This is not about whether or not he deserves respect. My problem is that instead of attacking his politics Dan Savage and others decided to mock Santorum by name. I simply looked at Santorum's Wikipedia page and discovered that he supported waterboarding (he defended it claiming it helped find Osama), he is against GLBT rights, he wanted to include intellegent design in No Child Left Behind bill. There are so many things he has done/supported that could have been attacked.
This is just childish.
It's not an either/or proposition. You can criticise his views, and you can make fun of him endlessly, assuming you're not one of his political opponents but just some minor person commenting on the situation (like Dan Savage). If, say, Romney had started the Santorum campaign, then it would rightly be considered a stupid and childish political manoeuvre. But it was just a joke between Dan Savage and his readers that happened to catch on. People have every right to make fun of other people they consider stupid, vile, hateful, or just ridiculous. That's kind of why this place exists, in fact.