Fair enough, I have not and was going on hearsay, but from wikipedia "As time passed however, scholarly reviews became more critical, chiding Carnegie for being insincere and manipulative" (https://en.wikipedia.org/wiki/How_to_Win_Friends_and_Influen...)

And it also says "Charles Manson used what he learned from the book in prison to manipulate women into killing on his behalf" but I don't know if that can be blamed on the book.