Joan Rivers' PETA Problem -- Screw You, My Furs Are Older Than Me! (VIDEO)

Joan Rivers lashed out at animal rights protesters at her book signing Tuesday ... insisting she's exposing the dead animals on her back to culture.

Joan was at Barnes and Noble in Times Square hawking her new book, "Diary of a Mad Diva" ... when someone from the animal rights org asked her why she insisted on wearing fur.

Joan seems stumped at first ... then lashes out.

And then the twist ... Joan seems to say she's not in the market for buying new furs, but she's not opposed to wearing the old ones.

Joan tells the crowd the furs have 2 options ... her basement or The Met.