Oh no, I totally agree. I'm more offended by the word "f****t" than I ever will be of the slang usage of "gay." For me, "gay" does not inherently carry bad connotations. It's a sexual orientation by definition. However, "f****t" is inherently a slur, meant to offend. I just found the graph kinda funny. Sorta cuz it's true.
I tend to not get offended by 'words' but how the words are expressed.
'f****t' as a word offends me for the reasons you state - it's a personal slur. However, I saw my cousin and his friends 16-17 years old and they were throwing 'gay' in there meaning stupid. I warned them at University to avoid using that. But I don't think it's something should be encouraged... the etymology of words can skew off into weird places in a short period of time.
I mean, look at the word 'gay', it only took 30 years for gay to stop meaning 'happy' to mean 'homosexual'...