I'm with Beloz, I HATE dogs crowding the gate too. Our park doesn't have double gates, just the one, and dogs are forever getting out because they barge through when somebody tries to come in. My dogs are very friendly but still refuse to walk in the gate if there are dogs crowding, it is intimidating for them. We always wait for the dogs to go away or for the owners to come and move them away... My dogs are always called away from the gate when a new dog enters, and are not given permission to say hello until everyone else says hello and moves on.. I don't want the dog getting crowded, scared and snappy.
There is a huge difference in the intimidation level of a rotti, gsd etc and some small dogs - it's stupid to think that it's not. Beloz did nothing wrong, I would have done the exact same thing. There is also a difference between polite sniffing and shove-the-nose-right-up-there sniffing which a lot of dogs hate- mine included, Meika will usually growl and run away and Molly will just roll straight over, but they are both capable of happy meeting dogs provided that the other dogs have basic manners and are under control of their owners.