Gates dutifully carried out whatever agenda the liberals handed him regardless of if that Liberal was an R or a D. He did so much damage to the military it may never recover. Had he any integrity he'd never have served under Obama to begin with. Same goes for anyone officer rank or above. ESPECIALLY Pentagon level brass. They all stood down when it was time to stand up, shirked their sworn oaths and helped advance leftist agendas.
I don't know enough about Gates to have an opinion but "Trump is "stubbornly uninformed" about the world." is a legitimate criticism. It has been often noted on this forum, Trump seems allergic to the kind of in-depth study he needs in order to be president.
But Trump's response: "we had a clown today, an absolute clown, Robert Gates...he's a nasty guy, probably has a problem we don't know about" is so unpresidential, juvenile and automatic. He calls Gates a name like some grade schooler. He implies there is something wrong with Gates. There is no reasoned response here. This is the lizard brain automatically spitting venom because someone dared to criticize. Think about it. To set off chaos in the US, all some foreign dignitary would have to do is reference President Trump's short fingers.