Working from the fact that it was only 2 second, I would respond to everyone that 2 second is not that long before the other guy starts in with a rude comment.
This other guy is basically shutting down the range for his own benefit and because the OP does not respond "fast enough" within this 2 second time frame, he is going to make a rude comment. Maybe the OP is an older guy,or maybe the hearing ain't so great as is common with shooters, or maybe the guy is just busy putting the gun in safe mode and is concentrating and not going to talk while making the gun safe. When I am clearing a gun and makeing it safe, I am not shooting the sh_t with my buddies, I am concentrating. Maybe the other people have ears (protectors) on and don't hear much.
The other guy could have and should have restated the request for asked for confirmation with out the smart langague or could have walked down the range to check with people and say hi.
When you are shutting down the range, for your own benefit, and making everyone stop shooting then you can at least give a person more than 2 seconds to respond. So if the OP does not jump to attention and say "Yes, Sir safe mode" then he gets called out. That is not very high road, IMO.
The other dude needs to relax a bit. There is no fire. If someone asks people to do something and then rides their arse if I don't respond within 2 seconds, all while the person is doing the task, that would make a crumby boss and a crumby person to be around.
Heck it takes me 2 seconds just to stop what I am doing and processing the info, let along formulate a response. Count to 2, it not a long time.
Are you all really saying that because he did not respond in 2 second, the OP is in the wrong? The problem was the other's smart arse comment. If the other guy would have said something nice or nice second reminder there would be no issue.