He didn't like to be trapped and moved by force. Even if you weren't being rough he had no choice in the matter which can make a dog defensive. He just wanted you to let go, he probably had no intentions of biting you to cause serious harm, it was most likely a warning bite but since he's a pup without bite inhibition he didn't know how hard was too hard.
I would start getting him to like have his collar grabbed and teach him that when he is led by the collar he gets super awesome treats. When it's time to go outside (if he wants out) bring him out by his collar. Maybe bring him to his dinner by the collar. And then set up actual training sessions where you grab his collar and then deliver a treat over and over and then move him by the collar and give treats over and over. Soon collar grabbing will not only be a normal, everyday thing he may even see it as a positive thing.
until you do some of there training sessions (starting with slow, gentle collar grabs under his neck, not over his head and progressing slowly to over the head slow grabs and then to under the chin fast grabs, then over the head fast grabs, then increased roughness etc.) never grab him or lead him by the collar. Use a leash, you won't have to lean over him when you move him, you will walk at a more normal pace with a normal stance and he will be less trapped. Also work on teaching words that you can use in the future to move him, things like come, off (of furniture), back up etc. are great commands to use to communicate to your dog so that you don't have to get in his space which can be threatening to a dog.
I most certainly think a dog should tolerate collar grabbing because sometimes it has to be done, emergencies happen, dog goes to grab a pill you dropped or bolt out the door and you might have to grab his collar, but it is in no way a gesture they naturally accept. They must be desensitized to it (using positive association aka TREATS) or socialized to it (if young enough that it does not bother them yet, this is simply exposing them to the action over and over so it becomes no big deal, there does not need to be positive association so long as nothing bad occurs in conjunction with the gesture, they just need to have a lot of exposure to it. This is not an option for you as your pup already dislikes it).
I also agree that tug does not cause aggression. In fact it is a useful game for dogs to learn to control themselves in stimulating situations. The dog has to play a stimulating game of tug AND has to watch his mouth. If his teeth touch you he broke the big rule and the game ends, so the dog learns to watch himself. The only time tug could cause biting problems is if the owner allows the dog to slip and bite the hands during the game without ending the game, the dog learns that hands are fair game, just another toy. So long as biting (even accidental) is not allowed in tug it's more useful than harmful IMO.
I know you must be very hurt by what your pup did, I can't imagine what it would be like to get bit by your own dog but remember he is just a "child" and he was scared and/or uncomfortable. I would in no way say that this makes him dangerous but it does need to be addressed so that it does not continue especially once he's bigger, if he gets to rehearse this biting behavior over and over he will learn that it is a very good way to get you to stop doing things he does not like so it's best to prevent putting him in situations he finds uncomfortable until you can desensitize him to them and teach him to accept or like them through positive association.
Good luck with your pup, they can be a lot of hard work but it'll be worth it in the end!