I predict that this thread is going to go downhill and be closed very quickly after that post.
Nevertheless, let me add my two cents worth.
No one, male or female, deserves to be the victim of violence.
I, too, have seen women push men knowing full well that he is going to resort to violence, and I don't understand the dynamic at all.
As to the OP's situation, if I were in his shoes, before anything else, I would have discreetly asked the bystanders if they knew what was going on. From what I have seen, the best way to intervene in these situations is with a non-aggressive response with non-verbal cues. A "tsk tsk" and a judgemental shaking of the head lets the attacker know that his honor has been questioned because of his behavior.
Also, keep in mind that intervening publicly can actually make the situation worse for the victim. If the aggressor becomes enraged because he has been publicly embarrassed because someone bigger and stronger has intervened, he may very well blame his victim for his humiliation. The lesser of two evils is that he hit her a few times in public to prove his masculinity than to kill her privately to defend his honor.
If you see that the abuse has reached a point where the victim's life is in danger, the best way to defuse the situation is to appeal to the aggressor's sense of self-preservation. Ask him if he thinks she is worth going to prison for. Tell him that he has proven his point.
Please be aware that I do not condone this behavior and I believe the reasoning in the mind of many aggressors is convoluted. But the dynamics of domestic violence are complicated, especially in a semi-lawless machismo culture, and each situation is different. If one chooses to respond, please do so in a way that does not make the situation worse for the victim.
More than anything, that is often why Dominicans will not directly intervene in such situations, resulting in the OP's question.