It's a sad, sad world we live in when an orange bean with a sombrero and a mustache is interpreted as being "racist."
I personally believe it all has to do with the comedy factor. Just because it's a stereotype that has been used ever since the advent of cinema doesn't mean it's racist. I mean, I could have a black guy with lips the size of Texas and the ability to jump really high and be extremely talented at rapping isn't racist, and a white guy who wears lots of gold chains around his neck, makes lots of gang signs, wears a backwards cap and is desperately trying to imitate the black guy, then's a stereotype, and a hilarious one at that. On the other hand, if I have the black guy wearing nothing but a potato sack and picking cotton out on a plantation field, and the white guy whipping him with a cat-o'-nine-tails repeatedly, then that's racist, and just not funny.
My point is, how exactly is an anthropomorphic mustachioed orange bean wearing a sombrero racist and offensive towards Mexicans? Is it the sombrero? Yeah, sombreros are a Mexican invention, and I'm sure millions of them wear sombreros every day. The mustache? There are no laws or regulations against facial hair. The beady black eyes? Beady black eyes are a common trait among all humans, not just those of Mexican descent.
In addition, your point that "it could stereotype Mexicans being beaners with sombreros and their mustache" is completely unaccounted for. If we look at the context of the above example, with the black guy and the white guy, we can determine that it's a stereotype, but it's a funny stereotype. You take a Mexican guy and dress him in ordinary street clothes, then it's just a Mexican guy in street clothes. Now put him in a sombrero and a mustache and have him say "qué pasa" every other sentence, then people instantly think it's funny. And if you think being funny is "racism," then I can't help you.