It's actually the opposite of ad hominem - I'm addressing his beliefs, not him as a person.

I recognize that he's contributed value to the OSS community, but over the last decade or two I think he's done far more harm than good. A number of his beliefs and writings are extremely problematic, and turning a blind eye to it because of his contributions taints the OSS community.

Another example:

"In the U.S., blacks are 12% of the population but commit 50% of violent crimes; can anyone honestly think this is unconnected to the fact that they average 15 points of IQ lower than the general population? That stupid people are more violent is a fact independent of skin color." -Eric S. Raymond