On some level, you can't help but be impressed by its regularity.
It comes up with surprising frequency in all settings, with discussion, with debate, in words spoken, in words written -- any time the prevailing ideology of a minority is challenged by one of its members.
As a perjorative, you can't beat it. It is designed to effectively and completely undercut whatever argument another has, blowing away any support in a nuclear fashion by painting the person as the worst of all reviled creatures -- a traitor. Someone who has sold others out for their own comfort. Someone who lives in luxury while their fellow minority members starve and suffer. Someone who supports the system that oppresses their fellows.
And gays, being expert practitioners of minority politics, do the same -- against, not just people like me, but, through innuendo and insinuation, even noted gay authors who don't toe the party line.
But as it turns out, all that's displaying is how few of them have actually read the book -- as an article from Ferris State University's Museum of Racist Memorabilia demonstrates. Indeed, as Dr. Patricia Turner, whose book Ceramic Uncles & Celluloid Mammies is cited therein, points out, the prevailing view of "Uncle Tom" is, in fact, a perversion of the original; Uncle Tom, throughout Beecher Stowe's original novel, is held up as an example of someone who is courageous enough to endure horrible pain, and ultimately death, to stand up for what he believes is right and to protect those who have been treated unjustly.
Furthermore, as the article goes on to point out, if you've been called "Uncle Tom", you're in good company; so have individuals like W.E.B. DuBois, Louis Armstrong, Jackie Robinson, Bayard Rustin, Arthur Ashe, Cornell West, and even Martin Luther King Jr. himself -- all criticized and lambasted by militant and hateful people because they refused to excoriate white people and to keep silent about the wrongful behaviors in their own communities from which the Tom-callers were benefiting.
So in short, the next time you're called that, keep in mind that you're being compared to a man who refused to hurt others even when doing so could have brought him advantage -- and was willing to die to protect those who needed it.
Then think of the commentary it makes on the erudition and motivation of the Tom-caller.