@Famine hit this from one side, which is that we do in environments where it is needed. But there is another side to this, which is that the standard that gets applied here is negligence. Normally, you don't walk past 1000 signs saying masks are required/encouraged and 1000 PSAs spammed to your phone, the internet, TV commercials, radio, and just about every media you can find letting you know that you're endangering others by not practicing social distancing and using masks.
So the act of walking into a grocery store without a mask is significantly different in that environment, the environment where everyone is letting you know that there happens to be a pandemic going on which is causing a lot of harm, and that we know how to stem the spread than the same act would be if there wasn't a pandemic and no one were letting you know these things.
The difference is that you know that you're causing harm and
ignoring that information if you refuse now. And acting in that manner is sometimes referred to as
criminal and for good reason.
Reductio ad absurdum is a valid way of identifying problems with someone's position. It's a
good thing. Not a logical fallacy.
It is the gist of the conversation. Businesses have restrictions on the manner in which they can operate to accept the public. We can debate those restrictions if someone wants to, but most businesses operating today could be said to have accepted those restrictions voluntarily, at least to an extent. At worst, you could argue that the licenses that a grocery store has to have to operate are an infringement on their rights. But invoking that contract and requiring masks or limits within the store is not necessarily a violation of the rights of the business owner. It'd be the contract itself (as long as that contract is what's being used) that would be the problem, and that was probably agreed to a decade ago in many cases.
So strictly speaking, the act itself of requiring those businesses to require masks is at least not clearly a violation of their rights. Although their rights may be violated in other ways. At no point does the general public really have any right to demand that they can wear certain clothing, or not wear certain clothing, to go into, for example, a grocery store. That's just not a thing. So when the government steps in and says "this clothing is required", it's
still not a thing.
If the government were to say that you have to wear a mask in your house, or in someone else's house, on their personal property which is not being operated under a specific use license with the state, that'd be a violation of rights. Otherwise the issue is with the license.
* Also, to really get into the weeds, some of those licenses may not allow the government to require masks. That's probably state or even city dependent.