I don't have specific references sufficient to convince someone who doesn't agree ("evidence"), but I have my reasons. I believe this probable, via feeling the negative connotation with "-ism" myself, knowing of other people who feel similarly, and understanding arguments for why such feelings could appear by association, so I don't need such references to hold the level of believe I have. The opposite effect (of "-ism" being beneficial) looks less probable for similar reasons.

My experiences agree. I have a memory of having talked to several people who've expressed notions of the type "anything ending in -ism is something to avoid", though these have been off-line conversations so I can't give direct references to them.