I think the typical player/collector would distinguish "scalper/toxic buyer" from a regular one is whether they use it simply as a money making/attention seeking tool and nothing more. Plenty of people buy cases of each set in a regular market, usually to collect some and possibly sell the rest. Those individuals have a general interest in the hobby beyond its profit making potential. On the other hand, a significant chunk of people buying up cards are doing it solely for the purpose of trying to make money. They think that just because some loudmouth loser on YouTube pulled a shiny card and claimed it was worth a mint, suddenly they can make easy money and get tons of attention in the process.
I do think the word scalper is being tossed around too liberally at this point, but people do have every right to be frustrated with wannabe investors making the hobby impossible for people who do want to enjoy the hobby even a bit. I also agree that the PSA move isn't some kind of heroic move on their part to stop the evil scalpers; it's an attempt to stop people from flooding them with submissions when they're already backed up by months or more. Sure, it may disincentivize a few people from buying cards since grading will be harder, but ultimately it's just going to punish collectors who were already waiting on their cards to be graded.