I've taken introductory philosophy class and my experience was somewhat similar. I remember my head getting messed with somewhat in the short term, as not so worthwhile lines of thought chewed up more of my brainpower than they probably deserved, but I think in the long term this hasn't stuck with me. I ended up coping with that class the same way I used to cope with sunday school: by using it as an a opportunity to note real examples of the different failure modes I've read about, in real time. I don't think you have to worry too much about being corrupted.