Of course they're less effective once they've become mainstream. As you mentioned, many slurs gradually lose any hateful meaning, and I'm sure the term "faggotry" might be becoming a bit less offensive over time, but seeing as how it's still used by many people in a hurtful way, it's not unreasonable to expect some people to be upset in situations where it's less clear. If someone disliked a comment using the term on 4chan, I wouldn't assume they disliked it for the term, but this isn't 4chan.