I think people just liked to blame BST when it wasn't always their fault. There were a lot of popular EXP camps in the crawler's nest back in the day. BST loved the place too because of all the charmable stuff in there. While BST were sometimes responsible for causing trains and wiping parties that were trying to test their limits, more often it was just a party wiping on its own and trying to avoid dying by running to the zone, which typically resulted in dozens of crawlers trained to the zone, causing anyone who entered the area to be KO'd instantly, especially if the train was from the knight crawler camps.I exp'd a lot in crawler's nest. There were so many places for BST to exp without being near parties that there was no need for contention there
That being said, I did have BSTs that dumped mobs on my party on more than one occasion, sometimes causing a wipe. So, while it is usually as you said, I have seen it happen because of a BST. It was things like this that led to the possibly unfair animosity towards bst and the eventual removal of monster trains.