<human>: While browsing reddit i came across a snapchat of a guy giving another guy a blowjob, the guy giving the blow job looked similar to me best friend's boyfriend, but it was obvious that it wasn't actually him.

My friend saw the picture and she thought it looked similar to her boyfriend as well so after a couple of minutes of us laughing and joking about him cheating she messaged him on Facebook. 

Friend: (Picture) Care to explain this?

Boyfriend: What is it?

Friend: That's you

Boyfriend: No it really isn't
                Hello?

Friend: That's you :'( 

He phoned up her after that message, and they argued. She tried to explain that it was just a joke and she knew it obviously wasn't him but he became defensive and said "This isn't something you joke about (Friends name)" After about half an hour of them arguing they stopped speaking for the day, but he sent a message a couple hours later
 
Boyfriend: "you not going to apologise?

Friend: What for?

Boyfriend: Sending that grim picture to me and trying to say it's me. It really got to me. 

Friend: It was a joke cause it looked a little bit like you, I'm sorry.

Could you distill the essence of the text into 1-3 sentences?
<bot>: Sent a friend a picture of someone giving a blowbjob that looked like her boyfriend, causing an argument between them and possibly their breakup.