Are you sick/injured/in the hospital? If you aren't, then you are subsidizing people who are. That's called health insurance.
Were you in a car accident? Is your car being repaired right now from an accident or incident? Was your car stolen? If your answer is 'no', then you're subsidizing the people who answered 'yes', that's called auto insurance.
Are you ____ or _____ or ______? If not, then you are subsizidizing the people who are. That's called ______ insurance.
Difference being that people more or less have to pay in under the ACA. I don't see a huge problem with that aspect, it's people's lives. Taxes already pay for other people's kid's school, other people to get rescued by firemen, helped by police officers, etc. Just like with health insurance, you might just need that help someday, so you pay to keep the whole thing alive.