thanks for explaining your position!
the difference here is a highly transmittable disease. So, you are ok with eating vitamins yourself, but not ok with doing something to protect the community. So, I see the priority here as opposite: someone eating unhealthy hurts primarily himself. And even as much as it is a Jewish thing to worry about each other, somehow we do not snatch the unhealthy food from our friends (maybe we should, and this stand-offish approach is goyishe influence). With Covid, behavior of one person affects health of others. So, if you are running a shul, you should do something to protect your kahal rather than ignore the issue. If you did not, then you have some responsibility for what you did not do. How is it caring about other people even controversial? Maybe that was the challenge that Hashem sent, some passed, some failed …
Just take this outside of politicized covid discussion. Was the person with strep that you described was an erloche yid walking around in public places, presuming he was contageous?