Earlier quoted context omitted.
"Slut" is a derogatory term, it has connotations and meanings well beyond the most literal definition of "promiscuous person". Calling Tinder user "sluts" is no more appropriate than calling my Chinese users "chinks", or my gay users "faggots". It seems intentionally obtuse to pretend that the term doesn't have a gigantic truckload of derogatory connotations behind it.
What are the negative connotations? I thought the only reason it was considered a bad term was purely because it was considered bad 60 years ago for a woman to be promiscuous. I.e. The insult was calling them promiscuous.
I can't speak for the whole world, but in North America at least I've never seen the word "slut" used in everyday speech that wasn't intended to be derogatory.
Side note: "purely because it was considered bad 60 years ago for a woman to be promiscuous"
I don't think that's 60 years ago, I'm pretty sure that's still today. Maybe not as bad, but the general perception of promiscuous women is still deeply negative.