Safety yiur gun for a moment and consider the pizza man. He knows someone ordered a pizza so wanted through the door to try and lose the pizza, maybe knock on some doors. I bet you could smell pizza too, huh?
Now consider criminals, if yiu were going to do a random home invasion, would you pick a multi story apartment building where neighbors are feet away, or a single famly home where theres more privacy and better loot?
Sure, keep your gun in your back pocket and stay ready and all that but damn, don't go condition red on the pizzaman in an apartment building! Let him in and maybe it was 6E instead of 6B (whatever)...if he steps out of line you can kill him without hate and quickly. ;-)
You didn't have your gun and would have drawn? Bad show three times. The third being, strive to help your fellow man in the face of your fears.
Wow, are you really that naive? You have got to be kidding! Let him in to knock on some doors? Cut him some slack? Really?
Security doors are there for a reason. You're supposed to assume that there is nothing of value in the complex because it isn't in the burbs on an acre of land? Wow, I am amazed! A pizza guy shows an aggressive move and it's all ok because he's on a delivery? Pass! He has a phone! Did he walk the pizza there? He can go to the car if it's cold to make a call. He forcibly made an attempt to enter a private residence, apt or not. A locked door is there for a reason. To keep the bad guys out.
Crack or heroin addicts live for the moment. They need $20 for a quick fix. They don't run out to the closest subdivision to rob a nice, big house. They go where it's close and easy. A delivery man is one of the easiest ways to get into a locked building.
You then ask "what did he look like". Wow, you are really out there. Tell me, what does a typical criminal look like? I'd say he could have just as easily pulled a knife or pistol from his pocket as you can. He could smell the pizza? So? That makes it ok? A bad guy looks like a man or woman who intends harm who probably has a weapon and will use it on you. I don't know, I'd guess that 5'8" 145# crack head looks pretty menacing with a .357 in your face.
You want to know who the scariest criminals are? They are the 14 and 15 year old kids who want to join the local gang. They have to "prove" themselves to get in. It often involves a crime against someone in the 'hood that makes the news. The kids have no fear of the law or their life. They do as they are told to be accepted. They are the ones you watch out for. Yeah, that 13 year old kid looks so tough and mean, huh? Geez.
I'd be willing to bet that the innocent pizza guy had other intentions because he did not wish to leave. The OP did the right thing in shutting the door in his face which may have surprised the guy. Aggressive delivery personnel are not the norm. I'd bet he saved someone from being robbed. The guy may have wanted to knock on doors looking for no one to be home or a frail, old lady answering. If he forced his way into the building I'm sure he'd have no problem robbing a little old lady. How would the OP feel if he read the next day that the nice old lady on the 2nd floor was robbed by a pizza delivery guy who he let in "because he was helping a fellow man". Wow, some people just don't get it.