There have been strict and harsh trainers in the series. However, they usually come in two types.
The first is the type that is unrelenting as a trainer but still deeply cares for his Pokemon. A.J. is a good example of this, for while he works his Pokemon to the ground, he still loves them deeply, and is loved in turn.
The second type is the arrogant trainer who has no respect for the sanctity of a trainer-Pokemon bond, and truly treats any Pokemon encountered like tools- often worthless tools at that. Examples of this class include Damien and Koji.
The important thing is that both types project the moral of caring for Pokemon. Trainers like A.J. are initially viewed as mean until their gentler side becomes apparent, showing that they still care about Pokemon in their own way. Ones that unrepentently view Pokemon as filth inevitably meet their just deserts with defeat, often at the hands of the Pokemon they abused. Therefore, the overall theme is that no matter what the training method is, the trainer must share a bond with his Pokemon.
Paul does not fit the archetype of this moral. He shows no repentance for the lack of love for his Pokemon. He had already given up on Chimchar when it faltered in the battle with Zangoose, and would have left it to certain defeat if it wasn't for Ash. Then he abandons it much like other bad trainers have in past episodes. The problem is that he never truly faces justice for his abuses. In fact, by the end his outlook is simply attributed to his style, disregarding that he added his own element of true callousness to training.
Personally, I felt that Paul was initially set up, like Hunter J, to be a counter to the show's morals. Such a conflict would certainly give the story drama. However, the full moral disparity was gradually forgotten, leaving his abuses as an unfinished plot.