Well, we shouldn't sing "Happy Birthday" at all, whether its someone's birthday or not. "Happy Birthday" is the most dour and depressing song that everyone knows. Berg, Schoenberg, or Webern couldn't write a song more atonal or dirge-like. YOU'RE NOT SUPPOSED TO SING DIRGES FOR PEOPLE'S BIRTHDAY.
I can't think of a thing that I willingly endure more regularly that causes me more pain that listening to people sing "Happy Birthday." Maybe the spinal tap I received while I was hospitalized. It's a toss-up.
Yes, you mean well. The road to hell is paved with good intentions, and sound-tracked with "Happy Birthday" on repeat.