I agree that xenophobic ravings like Tiernan's anti-Jewish slime-slinging should be outlawed, but that's more racist bigotry than "blasphemy" as such. Both these elements can certainly co-exist in the same statement, but one is not necessarily the other.

What worries me is not the muzzling of incitement-to-hatred rhetoric, but that this law casts such a wide and vague net that it's open to abuse. Never knowing whether you're on safe ground or not is intimidating - and there are no fear-police like the ones in your head.

I think Clontarf83 has it pegged pretty accurately - but the problem is not being sure. Because no one is exactly telling you.