I've never heard of proselyting as a word at all, so I'm going to guess that this might be a regional thing. I think the difference in connotation you are sensing might really be completely innocent, if so, and here's why: Most of the people on Hatrack/GC who are "proponents," as it were, of proselyting, live geographically close to each other, mostly out west. So they might tend to use the same word for purely regional reasons, while people who are not, say LDS or JW, come from a wider range of locations and may be more likely to use "proselytizing" for that reason. In other words, you may have a correlation but not a causality.