Sinclair - Why again is he a 'bad guy' ? :
Sinclair has lines in behavior he wont cross (certainly far short of where Fontaine or Lamb were willing to go - like killing people who were in their way), there are things he just wont do. He might be somewhat dishonest in his business practices, but "Let The Buyer Beware" is nothing new in the World, and is a part of personal responsibility which Rapture is much about. He is an Opportunist, but he appears to have largely worked within the law (perhaps why he came to Rapture with fewer of them).
You might say "He sold people to Fontaine Futuristsic for experiments or Big-Daddification" - but if you look at those posters in Persephone, that looks like it was volunteer (similar things happened in prisons 50s and earlier in the USA. with prisoners getting reduce sentences for volunteering for medical experiments).
With Persephone also being the City's Insane Asylum, or worse - where Criminally Insane people were dumped, there would be the question of (in a City where people are supposed to 'pay their own way') what to do with them for the rest of their lives and how to pay for them to be warehoused and cared for.
For insane people beyond help of therapy, employing them as Big Daddies to give them some work might be justified.
As seen with the 'Handymen' in Infinite BS it is possible that the City Worker Cyborgs (we will need to come up with a 50s term they were given before 'Big Daddy' ever existed) might include a number of physically disabled people who volunteered for their 'transformation', and kept much of their personality and free will (even the later Big Daddies didnt lose their minds -- they werent Robots).
Sinclair 'Art' is Business and Making Profits :
He is creative in his ways of finding new methods and paths to achieve his results.
He doesnt force anyone into buying his products or into accepting or following his beliefs.
Other people benefit by his actions and contributes to Raptures advancements.
About Sinclair :
Having him say this as if it is anything new in business processes is pretty distorted (trying to impart some kind of swindling sinisterness to something done in real business day in and day out) . People would be shocked if they learned how little things they buy actually cost in materials. What they dont realize is labor/process adds much of the value, and Sinclair has costs and risks and additional work/organization on his side to offset this assumed clueless 'syringe needle component price' versus the 'delivered to Ryan' price (as if it were all profit) distortedly being presented.
Sinclair should be more surprised that he doesn't have more competition (which in Rapture would make alot of sense and IS kind of dim to be omitted), as anyone else could do exactly as he does and could undercut his prices (and 'Ryan' WOULD buy the ones at the lower price...)
Sinclair was already rich when he came to Rapture and Pharmaceuticals was a real world way of making that happen (and at that time plant-based chemicals/drugs were a large source - something you really didn't have premade sources for in Rapture -- but Sinclair could using his previous experience/know-how with plants to bring them to be cultivated - and useful modern drugs would be something Ryan WOULD want for 'self-contained' Rapture). Having Pre-ADAM labs Tenenbaum worked in, meant Sinclair probably was already working in the medical (drugs? anti-biotics?) field....
Ryan actually had regard for proper competition ( "Offer a Better Product" ). So Sinclair also being in the ADAM product business probably would not make him Ryan's enemy (even better if Sinclair could figure out how to make the ADAM stuff safer, to cause less instability/damage). Ryan had all the rest of Rapture and his businesses to worry about. Sinclair might develop/market something different on his own (via his 'Think Tank' - "Selling Ryan Short"), or if it was too big a project, sell it to Ryan who had 'deeper-pockets' and who wanted to outdo Fontaine.
Remember, the ADAM industry was BIG with alot of different people/companies working on many different projects/products. So it would be highly likely Sinclair would not know all of what Tenenbaum was working on (particularly if it was something Fontaine wanted kept secret). Ditto for Suchong.
I will have to go back and read the Novel again. Those pages (p119) paint Sinclair in a better light than is portrayed in many parts of the Solo game - he is more mindful of 'civilized' conventions - lines that he wouldn't cross, and knew that people would (in Rapture) be held responsible for their actions - which is a major balancing component of the philosophy Ryan had.
Still, nothing in the game indicates if Sinclair was that much involved in the Plasmid business. Sadly, the series does not explore the (likely many) possible competitors for Fontaine Futuristics and Ryan Industries, and advertisements don't show any other name than theirs. Still, yes, the way Sinclair handled those tests both at Persephone and with the Consumer Reward Program, show he already had experience with the pharmaceutical market, and/or that he also used to conduct such tests prior to Rapture.
I don't think Ryan would have worked with Sinclair if the guy was double-crossing him. Also, Ryan Industries was providing Sinclair Solutions with experimental products for testing. If Sinclair had those (like Aero Dash, Geyser Trap and Houdini) sold on the market under his own brand, he would have been the first suspect Ryan would think of (besides the considerable expense Sinclair would have had to achieve any such production and marketing on his own).
Sinclair was a smart opportunist, but in the end he wasn't as much a monster as Fontaine was or seemingly Ryan became (or rather as the authors had to make him a cutout bad guy). Sinclair helping Delta to end his life in BioShock 2 showed that. The irony was he was made into one of the 'monsters' (BD) he had helped others create.
Anti-biotics were the latest things in World medicine around the time Rapture started and alot of the advertised ADAM products were medical related (I hadnt heard of Phossy Jaw before seeing one for curing that). So there probably were very many different/specialized products of just that kind (ex- we never got the name of the one(s) Steinman used for his surgery -- EZ-Slice-N-Dice, Good-As-New, Dr Sterns Liquid Suture, Scar-B-Gone ...) .
The industrialists/technologists/scientists/engineers who came also had skilled staff which many may have brought with them to Rapture (So Sinclair didnt do it all himself, but it sounded like he could understand all the very technical stuff). No doubt like Silicon Valley, as the industry expanded many would form their own companies off good ideas they got while working for others. So I dont think Sinclair would have 'double-crossed' Ryan, but would keep any additional business of his own seperate and might take opportunities in niches which Ryan ignored. Count how many Plasmids/Tonics were in the Gatherers Garden and think how many more there likely were (and how many may still have been just being developed/researched). Ones being sold to just to get rid of Migraines or Hangovers might have hands down outsold all the rest.