The tagline on the poster and home video cover for The Water Boy is "you can mess with him, but don't mess with his water". But the movie doesn't really have many scenes where people insult water to the title character. And he gets his "tackling fuel" by imagining people being mean to him like they always did, and hardly any are insults to water.
There's the scene at the beginning where a football player sprays him with water and he says not to waste it and would rather be physically attacked, but the player doesn't really insult water. There's a scene where one player spits in the water, leading to a flashback of a time when the same thing happened, and in the flashback he almost attacks that player before the coach stops him, and while this scene leads to Coach Klien telling him he has to stand up for himself which in turns leads to him showing how strong he is when angry enough, he doesn't attack the player who just spit in the cooler.
And his tackles come from him imagining people being mean to him, but hardly any of that imagining involves people insulting water or wasting it. The "water sucks, Gatorade's better" scene is the only exception (which the coach says just to give Bobby something to imagine on the field, as opposed to true malice). All of the other attacks involve him imagining or remembering people insulting him, his girlfriend, or his mama.
Hmm, I wonder if Bobby ever considered selling his own brand of bottled water after college.
The first one Bobby tackles is Gee, the member of the Mud Dogs to bully him the most, and he doesn't seem to change his opinion on him until later. On Bobby's first day of practice, after he had harmed him, he still insults him (giving him tackling fuel, though it wasn't his intent), after their first win, he makes an insulting remark about him to somebody at the victory party. When he gives his "we played as a team, we won as a team, and just because the water boy is a cheater doesn't change the fact that the real Mud Dogs will win" speech, I can't tell if he's actually defending him or if he's motivating the team and fans to have faith. Does he change by then, or when Vicki gets everyone to prove Bobby has friends, or is it just during the Bourbon Bowl, when he apologizes to Bobby once he shows up?
Captain Insano only appears in one scene, where Bobby calls in and gets laughed at when he finds out how old he is. And Bobby talks about him a lot, imitating some of his moves, but we never actually see Captain Insano wrestling. I guess a clever informed ability and way to work around having to actually show him wrestling. And if this scene happened today - a big-name wrestler laughing/mocking a fan on live TV - there'd probably be a lot of complaints from the public (trying to determine if that such fandom complaints would also occur towards all the football players who bully their own water boy).