The answer to your question happens to be, that it's like saying "people who eat donuts are quacky". Some are and some aren't. It has nothing to do with the donuts. A normal person who goes into a 12 step program - doesn't become wierd, the same way a wierd person who goes in, won't become normal.
Besides the point, if doing teshuvah, and really getting past this thing meant becoming wierd, you wouldn't do it? (And here comes the guilt trip) Is your sanity really more important to you than your purpose of existing? ie: Are you not willing to give up your sanity for H-shem?
I had that feeling for a long time, not just about 12 steps, but about all things having to do with idealism. Basically, whether you like it or not, if someone genuinely cares about anything for the sake of H-shem, or what is right - in our world that's considered wierd. You can wear tefillin, you can daven, you can learn, you can even put on a beard. But if someone loves H-shem... What's wrong with him? Did he snap? What is he Uncle Moishy or something?
So in the worst possible scenario, you can say it's going from true craziness - to normalicy, which unfortunately the world around you considers to be wierd.
I am very opinionated in this matter, so feel free to ignore whatever you disagree with.