It's hard to do nowadays, but it's still possible with small shops, especially if the owners are the same nation as you. Plus, you don't need to "racket" them - you can launder money through places with a small cut to the owners, there's tons of RP to do around that. You just gotta play smart. Even if you do it incorrectly, it shouldn't be OOC problem. If you fuck up in-game with your behavior or actions, police will get your ass, simple.
About CKs. I don't think that saying "no" should be a reason to kill the shop owner. You can destroy his business, you can shut him down (especially if you got ties in the government), etc. IF the shop owner gets you in trouble with police, reports you, records the conversation and then shows it to the government, then yeah - it can be a reason to brutally injure, or even kill him.
To conclude, I agree with people above - the extortion roleplay should be fun for both sides. You can even PM the business owner on forums and discuss this type of roleplay, for example if the business is directed towards a certain group of people (for example, a company that helps immigrants with papers/jobs). I don't promote scripted roleplay, especially if this roleplay is coming from OOC friends, but in certain scenarios the RP I described above can be fun not just for both parties, but for majority of players. Also, as I've mentioned, low standards RP shouldn't be illegal from OOC point of view. People, who don't know stuff about extortion and try it, will end up in cuffs anyway, so it'd be better to keep it IC.