I get that shit sometimes, one of the few things that piss me off. I work a "professional" job so I gotta come correct... I'm a lot more casual around my crew but my vocab and way of speaking combines both aspects of my life. People who don't know me don't understand that and expect me to be on some gangsta shit when they meet me. Nah, I'll talk world events, sports, music, etc with sense, but they expect me to be like the stereotypical black man on tv and just start yelling random shit to amuse them.
It's usually white people I don't know who say this shit (my legit white friends are cool)... If" acting black" means making a fool of myself just to amuse you, then you need to go find yourself a different comedian. White females don't usually say it but you can tell what they're thinking when you get into a convo with them. They don't want an intelligent black man, they want a certified G so she can go brag to her other friends about her newest acquisition.