Definitely valid questions.
I guess what I have in mind are two types of scenarios.
A. The newcomer/visitor who is out of the loop when it comes to Islam and the MSA at large.
B. Those who coming to the MSA or are already in the MSA not to change themselves, but to change Islam and the MSA
... these two people are very different as they come to the MSA with different intentions in mind. Now that being said...
With respect to my A scenario, there really isn't a line to be drawn. This person is sincerely coming to learn about Islam (even if they are not considering conversion) and if they show up half drunk in a bikini, they should be given the same benefit of the doubt (erm, maybe we can let the alcohol wear off :P )
My experience with these well meaning people though and it's only my experience, is that over time they usually pick it up the values and really try to respect them, often without being told. When they are told politely (if need be), they are pretty receptive and understanding. So with those sincere hearted people, we should work with them.
If someone does not want to pray, fine, but that's different then the type B scenario I have up top of the person who essentially has their own views of what Islam should be. Let A not pray, but someone, like B, if they want to tell everyone that prayer is not necessary and try to block off people from praying or try to organize some alternative prayer event, then that's where the person should be asked to leave.
I don't think there is anything to judge. While there is lots of gray in Islam, there is also a lot of clarify. Gambling trips are unacceptable, I think we all know that. Even if there are certain "types" of people, everyone in the MSA, particularly the eboard and event organizers, need to come to a compromise. Not everyone needs to express every aspect of their views through the MSA. If you're gambling kind of Muslim, then gamble somewhere else. I'm sure there are lots of things that all Muslims can agree on or find some happy medium on. They can organize social activities that are more acceptable, like hiking.
I think the bottom line though comes back down to respect. Regardless of where a Muslim falls in the conservative-liberal spectrum, respect those around you and find something else that's palatable for everyone.
Well ya, type A is going to return should be encouraged to come. Type B often has no intention of improving themselves.
In my personal experience with the MSA, most people I met were more like type A. First they come in tight fitting clothes, but they start to catch on and slowly you see some changes in them and that's great.
There was one lady who came to our MSA for awhile, she was the "progressive Muslim" type. Her clothes were not an issue, whatever, she wores jeans and sweatshirts. She always wanted to express her views and argue with everyone around her about her hijab was not fard and that sort of thing. Frankly, she was antagonistic, which nobody likes no matter what the issue is. Everyone was pretty nice to her but nobody really budged towards her views so she stopped coming.
Because you're a type A
Again, it goes back to my points of intention and respecting those around you. Most sincere people understand that when they come to the MSA, they are like guests, or if more involved, role models on some level or another. Just like a guest in someone's home respects the host and the role model is aware of how those view them, so too does the type A and these people with sincere hearts respect those around them.
My biggest contention is when the MSA itself, through its leaders, start to change the MSA into something that's not Islamic at all such as organizing trips to the slots. This is obviously a bigger (and different) issue than including newcomers who are not so aware. It's changing the organization to something that's simply not recognizable by its founders and previous leaders, which ANY organization would have problems with.
(Disclaimer: Please no one get on my back about the A and B classifications. I realize the world is more complex than this, but it's something I used to make myself more clear).