Shabbos Guest Who Dresses Inappropriately

What do we do about a Shabbos guest we have a lot who comes over wearing T-shirts and shorts? In our community, people customarily invite each other for Shabbos meals on a rotation to assure that no one is alone for a Shabbos. Most people without being told know the appropriate way to dress. For men, this is a collared shirt and long pants, either suit pants or business casual. But there is one young man who moved to our community in the past year who wears T-shirts and shorts when the weather is hot. Most people don’t confront him because they don’t have the nerve to do so. He routinely goes over the homes of others and also to shul this way, but no one does anything because they are not assertive enough to challenge him. I actually did last week and he told me in response it was over 100° and he wasn’t going to let himself die from the heat. It is true. It gets over 100° here a lot of the time. But this does not stop other men in our community from dressing appropriately for Shabbos. If they can, he can too. In my opinion, his yetzer hara is telling him to dress this way. The yetzer hara makes him feel uncomfortable, and he is failing the test to follow our community’s standards in response. If he got used to dressing appropriately, his body would acclimate and he wouldn’t die. We don’t want to stop inviting him over this issue because our community does not believe in excluding others.