I think you're missing the point of the original comment. Describing modern conservatism as a disability at once absolves conservatives of their responsibility not to hold abhorrent views, by classing it as a characteristic they have no control over, and lumps people with disabilities into a group that, in a non-insignificant number of cases, wants them dead or sterilised.

That's why the commenter was upset with you; not because you've criticised eugenics, but because you've been massively insensitive, and when someone pointed out that insensitivity you became defensive and attacked them in return.