See bolded above. So, it seems that you're saying that by someone inviting you to their wedding and advising you that more modest dress is the norm in their church, you actually think they're trying to push their version of Christianity on you? For the hour (or however long) the ceremony lasts?
You don't have to be friends with someone, you could actually be the blood relative of someone. I'm a convert to Orthodoxy, and I believe Mamabadger is, as well. So even if you had family who attended such a church who wanted you to share their special day, you wouldn't dress more modestly out of respect for them, because you thought they were trying to push their brand of Christianity on you?
To think about this in a slightly different way: if a friend had gotten you a job interview in her office, but warned you to dress more conservatively than you normally would for the interview (because of the office culture), would you think she was trying to push her view of the workplace on you?
The job analogy doesn't work. Either I'm interested in joining the corporation or I'm not. If I'm not, I have no interest in going to an interview. There is no compelling reason for me to hang out on company grounds if I don't want to join.