A friend of mine who se an old gay guy keeps harassing me for nude pictures. Should I give in or ? ?

Once you provide someone with pictures, you lose control of who else may see them.

No.  You should not give nude photos to someone who is pressuring You for the photos 

No, pictures can come back & bite you one day.

I find it so ironic that the generation I know of as the information generation as they have been using the internet their entire life,  yet they don't get it.

If you share any photo with anyone you give up control over it.  As an example.

If you give me your photo to look at there is nothing stooping me sharing it on line.

Once I do that its out there for ever.  It can never be 100% removed.

Clearly if this person wants nude photos he has sexual interest.  

What concerns me is that you are even considering his request. 

While we are at it.   In every country there are laws on the minimum age a person can be to be photographed nude.  In my country its 18.

If you are under that age and the police discover the photos and this could be today or in 40 years time,  you can be charged with having child porn despite you being the person in the photo and that pedophile sex conviction will stay with you for the remainder of your time.     If you live in one of those countries where the general population can look at peoples criminal history, all they will see is had images of a naked child. 

Lets see the pics.

No. He is not your friend. Tell him to never contact you again. And never let him blackmail you. Might do one thing and he’ll threaten to tell everyone unless you send nude pics or have sex with him. He might slip you drugs to get you addicted so you’ll do what he wants. He has no honor. He lacks judgement. He’ll do what he has to do to get what he wants for you or someone else vulnerable. Cut him out of your life. If he is a family friend - tell your parents. Show them proof. Tell your parents you never want to be left alone with him. And if you have little brothers - warn them.

Honestly - write all your interactions down with him over time. If he still harasses you - go to the police and get a restraining order. 

Sure what harm can pics do. As long as he doesn't live near you.

Why not send him some pics?

Old guys have needs too!

StupidFucking troll.