What's the difference between an "-ism" and "-phobia"?

Isn't an 'ism' in that context considered to be ignorance towards soemthing - like sexism etc, whereas a phobia is a fear of something.

Good question - and I'd say that there is a distinction between an ism and a phobia. If you take racism as an example, you can have racism and xenophobia, which are very similar.

Hmmm. Just scuppered my own argument there. I was going to say that the -ism can be out of ignorance, but the -phobia is an unconscious thing, but I don't think that argument works.

Gonna have to think on this one!

I think ism is a sense of being condecending/ignorant/superior etc towards something .while phobia is more of a fear of. Homophobia is normally used to refer to those who are anti homosexual cause of some fear or something (fear of unknown perhaps).
Besides homosexualism seems to imply - someone who is homosexual or having homosexual preferences.

Is a phobia an unconcious or uncontrolable fear whereas an '-ism' is something that a person has a choice over.

If, for instance, someone had a fear of spiders that could be considered as irrational, if you lived in England, as the chance of meeting a dangerous spider is remote. You could, though, have an '-ism' (i.e. hatred or dislike) over spiders (don't know what it would be called so not working out as a good analogy!) because you didn't like having to get rid of their webs, etc.

Therefore, I think a phobia is an uncontrolled aversion to a thing, object, whatever, and an '-ism' is a controlled hatred or dislike; both irrational?