It's an edit. In the original, the TV screen makes it look like the guy on the left is threatening the guy on the right (the foot looks like a knife). It's meant to be a commentary on how biased media coverage can essentially reverse the roles of the oppressed and the oppressors. And this edit was made to show how in America, republican media coverage tells people that the democrats are "sucking off" leftists, even though democrats don't agree on a lot of things with actual leftists in reality. The caption explaining all of that has been cropped of, you're just meant to know it, which is what makes this meme funny.

I think the dude is just watching porn on his TV stand while a murder scene runs by in the background.

its an edit. in the original picture the foot of the attached looked like a knife and the attacker like the victim.

It's not the original image, but yep it's not that funny when you have never seen the original