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.
I feel that the term "rationalism", as opposed to "rationality", or "study of rationality", has undesirable connotations. My concerns are presented well by Eric Drexler in the article For Darwin’s sake, reject "Darwin-ism" (and other pernicious terms):
So, my suggestion is to use "rationality" consistently and to avoid using "rationalism". Via similarity to "scientist" and "physicist", "rationalist" doesn't seem to have the same problem. Discuss.
(Typical usage on Less Wrong is this way already, 3720 Google results for "rationality" and 1210 for "rationalist", against 251 for "rationalism". I've made this post as a reference for when someone uses "rationalism".)