If I may shed a bit of light on the feminist perspective:
Firstly, there is no one group of "the feminists." Feminism is a collective of theories and approaches that are often vastly different: radical feminism, liberal feminism, intersectional feminism, and on, and on, and on.
Secondly, as a feminist, my position on domestic violence and sexualized violence has more to do with the systemic suppression and acceptance of such violence, than with the violence itself. Women can be assholes. Men can be assholes. Any combination of women and men, or men and men, or women and women, can be assholes to each other and inflict both physical and emotional pain on each other. In all situations, it is equally ed up and inappropriate, as far as I'm concerned.
The difference, however, is that when you have a situation in which someone in a position of systemic power (in this country: men) inflicts physical or emotional pain on someone in a position of systemic weakness (in this country: women), it perpetuates and reinforces the position of women in this country as an oppressed group. Especially when it becomes normalized or justified as acceptable or understandable. Or, even worse, joked about.
Furthermore, I have a problem with it in terms of social stigma and available resources. Chris Brown and Rihanna are both wealthy, so they're less of a concern in this regard, but for many feminists the domestic violence issue is particulalrly troubling for the many ways in which our society encourages someone to stay with a partner who is abusing them. And I say partner here for a reason: women who are battered by their male partners, men who are battered by their female partners, women who are battered by female partners, and men who are battered by male partners are all in the same boat, here. Our society makes it very difficult to admit that we're in this situation or to attain the help necessary to get out of an abusive situation. Especially in cases in which, for example, a wife may be dependent on her abusive husband's income to support her children.
That is (part of) why (some) feminists take issue with domestic violence. Not because we think women are delicate flowers in need of special treatment or protections.