The anti-MBA movement is really trying to redefine what an MBA means. Bad business decisions are "M.B.A.-ization". Good business decisions are... something else. Therefore, MBAs are bad.
There are plenty of bad MBAs running around, but it's no different than how we also have plenty of bad software developers out there despite having C.S. degrees. In both cases, the worst offenders are over-represented in the talent pool because they're more frequently pushed out of companies, while the best talent is locked up with high compensation.