Kinda sorta. I think there's a couple things at play here. One is that sometimes when someone gives themselves a title (like Mentalist), they come across as arrogant. If someone calls themselves something, they then have to live up to that title. Which leads to the second thing - If the performer doesn't live up to the title they give themselves, the audience picks one for them. That title will often be "magician". There is also the part where when those audiences see a "real" mentalist, their definition shifts. It's the same as when they see a "real" magician, as opposed to seeing Uncle Charley doing the 21 card trick or dudes just trying to get girls at the bar. When they see someone dedicated to their craft doing their thing, it raises the bar for that label. So, yes, bad performers of any ilk create a bad name for all performers of that style - but one good performer changes that.