Well Im a 'mature' student myself and I dont find that people distance themselves from me. Actually, theres quite a lot of mature people on my course, I think you'd be surprised at how many people there were: I reckon around half of the people on my course are mature students.
You may find though that a lot of mature students have other responsibilites that younger students do not, for example working aswell as studying, child care, living off campus etc, so because of those reasons, people may not be as 'accessible' as younger students, just because they have other priorities. For example they might not be able to go out drinking every night etc
If people dont want to be friends with students just because they're mature then thats pathetic, and to be honest I think you'll find that most younger students arent like that anyway, and tend to have large and varied groups of friends/acquaintences