Is Salamo 3alekom offending?

A few days before Ramadan, I was entering a building in Cairo. There were two men standing at the door, so I said, "salamo 3aleko". They did not answer, looked at each other and then they stared back at me. One of them looked down and shook his head.

"What?", I asked. One of them just laughed. "Is there a problem?", I asked again.

"No. Come in (itfaddal)".

About two hours later it occured to me that maybe the two men, who were bouncers, didn't think it was appropriate of me to say salamo 3aleko to them while I was entering the bar.

Personally, I don't see why not?