I generally think with terms like that, it's more of a warning to be careful using it. So a term like "lame" might be okay to use in like 99% of online discourse, but you have to be understanding if you hit the 1%, whereas a term like "f*g" will probably be problematic in effectively all contexts.

Or at least that's how I understand it. Imo, it's not that you should never call something "lame" or "dumb" in a disparaging way, but rather that you should understand that that usage has a problematic origin, even if it's almost guaranteed not to offend people, and that you should just be careful.