In general when going to a sim where everyone is in formal wear, I will change immediately to fit in. But, I have to say, I think the banning of inappropriately dressed avis is excessive. Ejecting is probably to be expected, if you appear somewhere and your avi doesn't fit in with the theme or is overtly offensive. Particularly with formal dress sims. But again, imho, unless someone is obviously trying to grief the sim, I think ejecting is a little over the top, and banning is excessive.
I mean, really, the saying "power corrupts and absolute power corrupts absolutely" is probably the case for some land owners. Let's face it, it isn't actual real life. It's pixels, people! Yes, I know many choose to build elaborate sims and I applaud them. And I understand their drive for perfection, even down to costume wear. But the banning behavior is, again jmo, a power play and slightly obsessive. These are real people with real feelings and you are preferring pixels over people at that point. Remember, there are lots of personalities in sl, and some people who have handicaps as far as reading, even as far as comprehending things. So it seems unfair that they should be excluded as soon as they appear on the scene in different dress. And it does tend to leave a bitter taste in one's mouth regarding sl.