Indeed, diseases like polio and measles are very harmful.
You have a right to ruin your health, the moral question is about taking other people with you. So I have a moral right to avoid you. Socialized medicine complicates things by making me pay for your idiocy.
As for where SARS2 breeds, indeed it is in more than humans - animals can get it, household pets and farmed min for example. Indeed it may well have come from bats, who tend not to be severely affected by it, but the suspicion a virus was enhanced in a laboratory is credible - no smoking gun either way yet.