Is it now acceptable to use "hung" instead of "hanged" in the sense of execution?

Agreed, in that particular case. But one is more correct than the other, and there really is a point to English grammar. As I travel through cyberspace and encounter more and more illiterates whose attempts at elucidation straddle the boundary of incomprehensible, and require an inordinate amount of my own effort merely to render their incoherent ramblings into an argument that is wrong, I find that ungrammatical language is basically just an egregious form of rudeness. At its core, it says that you’d rather be lazy than help your fellow man understand what the hell you are saying.