You don't have to be friends with everyone you work with; you just have to be able to work with them. If you get along with them/ are friends with them, that's just a bennie. I've tried to live by this since I joined the military years ago and would be so annoyed by many of my peers. This concept was greatly challenged in nursing school (much more so than it ever was in 8 yrs in the military). Especially by those with very, very questionable ethics, and the whining- oh God, the whining! The few people I became good friends with I actually have very little in common with, but we just got along. There was only one other mother- out of 40 students- and she lived far from me, and to be honest, just not my "type."
Group work was extremely painful at the beginning because we worked in assigned groups, but as school went on, we were actually able to pick who we worked with, to some extent, which really help. We knew each other's strengths and weaknesses and it made things flow so much better.
Also, it's great that you are not tied down to working for a salary, but for most people, that's just how it is, and it does seem like you are judging them d/t your "higher calling." I also enjoyed working with the homeless and am drawn to the ideology of community clinics, but for now, I work in a hospital, paying back my student loans and making sure my kids have everything they need (and a few things they want).
It was fairly easy to pick out those not worth my time and energy, and when at all possible, I just kept away from them. When I absolutely had to work with them, I was cordial, professional and made sure that an acceptable end result was obtained. Otherwise, they were really not on my radar.