In Avengers Mansion, Captain America sets aside his mighty shield to spell the weary Jarvis in opening the morning mail (maybe Jarvis got a paper cut):
All panels in this post are from Avengers #113,
written by Steve Englehart, art by Bob Brown and Frank Bolle
What's this? Why is Cap so confounded? Fan mail from some flounder? No!
So what is our star-spangled Avenger's response to this creepy communiqué?:
Yay, Cap! Now that's how you deal with hate mail! Nowadays we'd have a seventeen-part cross-over series in which Cap manipulates Nick Fury into hacking the USPS mainframe database to find the sender of this slimy snail mail, then enlist the Punisher to beat out of him the true mastermind behinds the devilish plot, who would probably turn out to be Iron Man with a brain slug attached or something. But in the seventies, this neat little piece of characterization tells us all we need to know in four panels: that there's still some ugly-minded, illiterate hate-mongers hiding behind anonymity to spew their prejudice against the American right of a artificial synthezoid to get smoochy with a Balkan mutant witch, and Cap don't put up with that crap.
I don't post on many out-and-out discussion boards like CBR or Newsarama, but I think that this would be a dandy response to post right after some of the dumb-ass statements made by fans and heck, sometimes even creators:
You da man, Cap. You, sir, are truly da man.