My response to that would be that it's really not your place or anyone's to tell someone how angry, or not angry, they should get about moral issues either in broad scope or one by one.
I'm not mad at you or anything, I'm just saying! Everyone has to make their own decisions about these things.
Also, argument to "concentrate on bigger problems than one ass shot," here's an alternate viewpoint: artists like Greg Land and Frank Cho clearly aren't going to change their style, well, ever. On the other hand, someone who just sticks in one ass shot may just be doing it because they were told to do it, or because it's the thing to do to get readers, or because it's practically a habit. If they, or their editors get told that there are readers who don't like ass shots, they might actually listen. And if the argument's put forth well enough, those artists and editors might keep that in mind for the next project they work on -- although that's probably a giant overdose of optimism, but you never know!