If a person has the virus they or anyone who lives with them should not leave the house. If they do it is extremely surprising, and those who think it isn�t are the problem. On the other hand, while everyone takes their own level of precautions there is no way to ensure everyone around you is safe to their standards. The reality is that everyone has their own understanding of what is acceptable, and each person will stretch their personal precautions when it comes to things they �must� do or places they �must� be. If a person is extra cautious they should not go places expecting everyone to be like them. The key is simply this: in general when seeing people, maintain a distance. In specific situations see what�s happening and decide if you want to be there or not, because you can�t change what people are doing.
There are plenty of good reasons not to wear a mask that would not effect others. (Recently recovered and antibodies, tested negative a few days before and haven�t been anywhere, plan to maintain a six foot distance etc.) If a shul requires masks then you must wear a mask. If they don�t then one should not be forced to wear one. And if that makes some feel uncomfortable they can either go around asking people why they aren�t wearing it to determine if it�s safe or not take the risk and find another shul.