Still disagree (based on very close dealings over the years), and especially since higher level promotions are not purely merit based. And to say "they" are not demonized might be true in front of them, however, liberals in general are demonized as a matter of culture in the military. Remember i am not talking about E-1-5 here.
If you're talking about enlisted promotions from E-6 through E-9, those are done by promotion boards that meet hundreds or thousands of miles away, where I don't think it's even possible for the board to know what the person's political preferences might be. There is no room in the selection process for them to consider that kind of stuff.
Regarding promotions from Major through Colonel, it's the same process: a board that doesn't even meet the individual up for promotion makes a decision based on officer evaluation reports, education, performance, physical fitness, etc.
I think general officer promotions could get "political," but by and large everything else doesn't involve discrimination based on political philosophy.