I've noticed a sort of conversational tic among political conservatives, that of declaring that someone has proposed the "moral equivalence" of two acts that are patently inequivalent morally. Once the existence of an attempt at an invalid moral equivalence has been declared, everything else the person might have said is treated as answered.
It's as though for some people the moral categories have collapsed into two, "Good" and "Evil," and all good things are equivalently good and all evil things equivalently evil. It's the reflexive style of thought of the soldier on the battlefield transported to the reflective environment of discussion and debate. The thought that two things can be similar -- both immoral, in this case -- without being equivalent is avoided whenever possible.
What to do, when discussing matters with people who exhibit this tic? You can avoid criticizing more than one thing at a time (per blog post, or op ed piece, or conversation). You can weigh down your words with caveats in an attempt to forestall the charge of invalid moral equivalence. You can counter the charges when they arise. You can ignore the charges. I'm not sure, though, that you can teach them not to insist you believe that all evil things are equivalently evil.