It's stupid. Neither was trying to be malicious or IMHO, racist at heart or anything close.
Both were attempts at humor (how funny is up to you).
I think Asher's was funny personally. I think a lot of people really overreacted to that one. It was by NO means racist.
John Mayer's was probably in poor taste. I'm not terribly sensitive in general, but the 'my d*cks a white supremacist' was funny to me and lots of my friends.
I think people play double standards all the time and it's unavoidable. However, when you are in the public light like Roth and Mayer your room for error is much smaller than the avg joe.
Which makes me wonder how much insensitive ish Joell Ortiz has said that no one's call him out on but now he wants to get made about a bad joke that wasn't anywhere near the realm of Imus or Kosmo Kramer.