as Kes says they are just stating their opinion and aren't actually expecting you to reply anyway.
Or they don't care what you say anyway.
The other night I had a situation in the box, a player did a roulette turn (fancy!) and went down under a challenge. I was no more than a few yards away, right on top of it, perfect angle. From my point of view, he spun around and his trailing leg (not his standing leg) made contact with the defender and he went down forwards. Now, if he had been fouled, I was expecting him to go backwards due to the nature of the move, and in any case, it didn't come close to his standing leg, basically it had every sign of a player seeking contact but not being fouled. So I shouted 'no foul, play on'.
His manager and some other club official all the way back at the halfway line? "Clearest penalty ever!" and they were adamant the defender took out his standing leg.
So, two guys, from fifty yards or whatever back have a better view than me? And even when I explained what I saw, they dismissed it and it's my fault and I'm clearly blind and so on and so forth.
To be fair, I don't really care if a manager/player disagrees with a decision, I understand sometimes people have different views on what is a foul or not, and I said that to them 'fair enough, that's how you see it' and I already gave my view so I wasn't entertaining it further. Post-match though, wouldn't let it go so I sent the manager off.
You just can't win with some people.