Charlie Sheen just UNLOADED on President Obama -- tearing POTUS apart because he filled out an NCAA Final Four bracket ... and telling TMZ Sports, "We deserve better from our President."
Earlier in the day, Sheen had posted a tweet -- in which he rips Obama for making college basketball picks instead of attending funerals for soldiers.
"It's not cool," Sheen said ... "I don't care about the picks. I care about wasting that kind of time when the world is in the state it's in right now."
"We deserve better from our president ... and I demand it!"