I've been told the same thing--that I'm rude, conceited, condescending, etc. If I knew a way to 'tone it down' I probably would, but I don't know how. If people are only saying this because you use big words, then I would ignore it. A problem I have that makes me seem like a know-it-all is I feel the need to correct people and I'm trying to work on that, but not doing very well I would try to notice if you do the same thing.
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After a time, you may find that having is not so pleasing a thing, after all, as wanting. It is not logical, but it is often true.
--Spock