You are entirely spot on in what you say. My own initial reaction towards the dog abuser was of hatred, which isn't bad in itself - it would be strange for us "ordinary" folks not to have knee-jerk reactions under certain circumstances. It's hard to watch a video like that and not feel a loathing towards the abuser.
However, if we think about our anger in terms of wishing the abuser becomes harmed (or faces death as a punishment, as some of the petition's signatories have called for) and if we still hold these thoughts long after our initial shock, then how are we any better than the abuser? Whatever someone does, by calling for their suffering, we are still calling for the suffering of another being. Would Buddha have sought this? Would Jesus or Krishna? No.
If I may say so, the only thing I'd say people might misunderstand is the idea of "loving" such an abuser. This is understandable - very few people can open up their hearts like that and so, I personally find a progressive move towards that sort of ideal is best. So for example, for those who would call you mad for suggesting we feel compassion towards "evil" people, perhaps it's better to explain how their anger only harms themselves - the abuser doesn't feel my anger...what good is it doing? If we can direct others towards compassion progressively, they are more likely to arrive at their own understanding of compassion towards themselves and others.
Of course, in practical terms, you can't kill/jail a problem. Education, raising awareness and appropriate penalties should instead be put in place. You can jail/kill the abuser, but you can't jail/kill abuse. The only way you can reduce it (and significantly) is if we tackle the root of abuse or any other crime, and that is only done through understanding, awareness and education.
For what my opinion is worth, I think your points are completely valid; it's just a matter of keeping in mind that others might not see things in the same way, and approaching a subject or situation in a way that leads to better understanding. By saying we should be loving towards these abusers...man, you're a freak!
(I jest, of course).
I think it's also worthwhile keeping in mind that there's no such thing as an "evil person"; only a person who performs an evil action.