He assured me that I didn't need to "check with my son who does all my computer work" before doing this, since he was "from Microsoft" and that if my son uses the computer, he may actually be responsible for those infected files on my computer.
I had some choice words for him, having lowered my voice throughout the call so he would have to listen closely. He said that he had turned his volume up all the way and that I needed to speak more loudly. Trust me, I did. And very clearly.
Warn your parents that Microsoft won't call.