I have to agree with Deadeye here. The scene is told through subtleties.
0:11 The stare down (Marlo feels a way bout it)
0:21 - :27 Marlo steals knowing he's being stared at (returning the disrespect)
0:41 - :51 Guard tells Marlo how hes a hard working man supporting his family (marlo out here trying to get it too, so what)
0:51 - :58 "Pretend I'm not talking to you.. like i aint even on this earth. I know what you are" (sounds like the guard is saying he's a better man than marlo)
1:06 Guard steps in front of Marlo face as if to impose his presence. This is what got him killed.
"You want it to be one way.. but its the other way" .... The guard wanted Marlo to give him respect, though you can say he didn't give respect when Marlo walked into the store. Then he gets into this "valor" bullshit whiteface talking bout, how he's a working man with a family so that's the reason Marlo is supposed to give him respect. You can suspect Marlo comes from a very broken family so this means little to him. But then the step up.. Marlo comes from a background where he's snatching respect, because it aint given. On some street shit, some1 imposing their presence is to be taken as danger, you can't say its not a threat and suddenly its not. The security guard violated all the nuances that come with street shit, the disrespect, the belittling, then imposing your presence... He thought being a working family man that "stepping to" was a means to be given respect, in Marlo's world it's a polar opposite. "You want it to be one way.. but it's the other way"
From the moment Marlo stepped in that store, the security guard looked him up and down with contempt. Sounds like ego to me.