I am told by those who may actually have a reason to know that Under Armor tee-shirts and tank tops work pretty well. I don't know anything about the politics of the company, but I would suspect a degree of left wing lunacy, just because. Haven't worn Levis in years because of their idiotic politics. Won't use a Leatherman multi-tool, either. I was a little p-o'd at USAA when they cancelled sponsorship of Hannity, but I feel a little better about them since they also cancelled sponsorship of Mad-cow. Tough to keep all this stuff straight.
My limited research comes out of Florida where we have reason and inclination to sweat copious amounts.
Disclaimer: I have not tried Under Armor.
FWIW,
Crusader Rabbit