John Lennon's angry letter to Paul and Linda McCartney up for sale

A letter typed by John Lennon to Linda and Paul McCartney in 1971 is up for sale with the RR Auction house.
The note is un-signed and expected to reach a price of $20,000. 
The angry letter was written in response to a letter sent from McCartney's wife at the time, Linda.
Lennon began responded to Linda's letter saying he wondering what middle aged cranky Beatle fan wrote it. 
The letter has hand-written annotations from Lennon and includes insults such as 'Get of your high horse' and 'Who do you think we/you are?'.
Lennon goes on to say “You really think the press are beneath me/you? Do you think that?”
“The ‘self-indulgent doesn’t realize who he is hurting’ bit—I hope you realize what sh-t you and the rest of my ‘kind and unselfish’ friends laid on Yoko and me, since we’ve been together. It might have sometimes been a bit more subtle or should I say ‘middle class’—but not often. We both ‘rose above it’ quite a few times—& forgave you two—so it’s the least you can do for us—you noble people—Linda—if you don’t care what I say—shut up!”
He ended the letter with: “GOD HELP YOU OUT, PAUL—see you in two years—I reckon you’ll be out then.”