BT: I took a year off of tennis once because I'd get upset and swearing just generally feeling crappy after playing.
I came back to it really enjoying the sport and I made up one or two funny sounding fake swear words that didn't carry the burden of pain with them. I don't use them much now but in tight spots.
You don't know what your opponent has gone through in the past, I gather, and perhaps he, too, went through a period of negativity. . . and thus your actions may well have made him feel pulled into that negative place again, perhaps after he'd worked to get himself out of it.
So he might be more sensitive than you thought.
Heck, that's my stab at it.
To Praise, To Bless, To Preach--the Dominican Order