I'm not online much, but most of the anti-LBT stuff is directed toward the sequels, not the original movie. They believe that the sequels are profit-oriented ripoffs of a classic hoping to capitalize on the short-lived "anthropomorphic dinosaur" fad (which spawned such titles as Dink, Disney's Dinosaur, and We're back!). However, what makes LBT different is the fact that it is still around while the others died out when the fad ended.
There are also those who dislike sequels 6-13 because they have become more campy and kid-oriented, supposedly losing the feel of the original completely. In TV, the term is "jumping the shark," though I don't think the term applies to video sequels (probably because most movie series don't get more than two or three sequels). Since this argument is more opinion than fact, there's no real way to debase it, other than to point it out as a logical fallacy.