While Corbett seems to have a tin year when it comes to public sensibilities, I don't think this is fair.
A suggestion was made that recognizing homosexual marriages means opening a Pandora's box of immoral activities being sanctioned. Well, no - Governor says - the gay marriage does not bear any resemblance to the situation when the marriage contract is being imposed on someone incapable of entering a legally binding contract - for a reason of being a child...or, for example, a goat.
The situation of adult siblings wishing to marry is, indeed, rather similar to the gay situation - at least on the level of the objections being offered.
There's a strong societal taboo against incest, and a darn good biological reason for it: Children are very likely to pay with their health for such union. But, in the age of contraception and especially after we admit that "marriage" is not primarily about child-rearing, what exactly is the objection, rationally speaking? Our instinctive disgust? And? 30% of the population may be "disgusted" by the idea of homosexual marriage; 85% - by the idea of sister and brother marrying (in this society; didn't bother Ancient Egyptians or not-so-ancient-Hawaiians in the least).
There's no popular demand to make sibling marriages legal, and none is expected in the foreseeable future. Also, my own position (decidedly FOR gay marriages, if "civil unions for all" is not an option) is not likely to be influenced by this kind of rambling discourse. But let's try to stick to some elementary fairness here: What the guy said was actually quite correct. It just was. Regardless of who he is, or what his hidden agenda may be.
Your outrage is entirely a predictable result of your partisan expectations.