I understand this sentiment. If you survive and come out mentally okay and even improved, was it really a bad trip?
The problem comes when the drug takes such an effect that you aren't able to remind yourself "This is the drug doing this to me."
Sometimes, a bad trip doesn't even have to be ego death or an uncontrollable hallucination. Sometimes the physical effects lead someone to bad trips.
For instance, for a couple of years every time i would trip at one of my friends houses, the trip would usually end up in his basement at some point. Now let me get this out there; I'm not a pet guy. Dogs, cats, doesn't matter. Don't like them. Not afraid of them, just don't like the smells, the barks and especially the loose fur. Anyway, inevitably we would end up in my friends basement and he has 3 dogs. It's not a nasty basement by any means, it's actually incredibly clean. But every single time i would get the feeling in my mouth that I had a rogue dog hair on my tongue. It would drive me absolutely crazy. And if i wasn't sober enough to remind myself that it wasn't real and the acid was just fucking with me, I can easily see how that level of physical discomfort could lead an unexperienced tripper or someone tripping harder than me to have a terrible time.
My one truly bad trip on a psych was definitely caused by a mixture of the potency of the drugs and everything leading up to tripping.
It was my 3rd time tripping. My first 2 times tripping (on 2g to 3g of mushrooms) were life changing shit. More fun than I even thought was possible. Still 2 of the best days of my life. And they were both at the beginning of summer. So for the next 2 months, every waking moment of my life was dedicated to finding more mushrooms. It consumed me. I wanted them so bad. And in August, we finally got them. I thought I was invincible, so I doubled my dose. Took probably 4g's of some big, scary looking mushies. Probably 5 of us took them, with 2 (1 of whom's house we were at) of my other friends not partaking. Eating them was terrible. These things were huge even dried, and I thought, "Hey, what would be the best way to eat these things? With marshmallows and chocolate syrup!" Wrong. It made them way harder to get down. 2 of the other people tripping with us had such a hard time eating them that they threw them back up.
So we get them down and we're sitting on a giant haul trailer in the middle of the yard, listening to music and getting ready to have a great night and here come my 2 non-tripping friends with boxes on their heads like 2 dipshits trying to get us to freak out or something. Obviously it didn't work and I told them how dumb of an idea this was. the non-tripper who's house we were actually at didn't like that at all. And he was pissed. Telling us all to leave and that we shouldn't even be doing drugs at his house. Mind you, he was one of our really good friends, so we didn't actually have to leave. But this encounter really set a bad precedent for the night. Then cars starting rolling into the driveway and he said that he was gonna have a party while we were tripping. Which pissed me off even more because..well, who the wants to have a great trip ruined by all the worst people you know getting drunk around you?
Long story way shorter, trip was 5x more intense than anything I ever encountered. I thought I died yada yada yada ego death yada yada yada came to yada yada learned a lot about myself yada yada. I also think the mushrooms and my brain were teaching me a lesson. Yes, they are insanely fun. But they are absolutely big boy shit and not to be taken lightly. At some point, they're stronger than you. And you need to realize that.
Point is, set and setting have A LOT to do with bad trips. But no matter how good the setting is, there comes a point where you can't distinguish real life anguish from what the drug is doing to you. And that's scarier than hell.