We typically sit near home plate -either slightly to the 1B side or 3B side depending on whether the team is home or away. Unless the "cussing" is right in the plate area, I rarely can hear it if it comes from anywhere past the pitcher's mound. And even around the plate, it's hard (for me anyway) to pick up.
Those that are "cussing" such that you can hear it from the stands really must be vocal!
I don't recall any ejections specifically for inappropriate language. They've all been for other reasons - cleating the catcher in the chest, throwing helmets, throwing bats after a strikeout call, etc. There may have been some language tossed about, but most times no one in the fans could really hear it.
I can say I've heard far more inappropriate language from the fan side than I have coming from the field. Especially during HS football games.