Facebook Inc took down a popular Wall Street discussion group, Robinhood Stock Traders, in a move that its founder on Thursday described as backlash for conversations buoying shares of GameStop Corp and other companies this week. GameStop, AMC Entertainment Holdings Inc and BlackBerry have been at the center of a market battle as individual investors coordinating on social media including Reddit, and using trading apps such as Robinhood, bought shares and squeezed hedge funds that had bet big on those struggling companies to tank. Allen Tran, a 23-year-old from Chicago who created Robinhood Stock Traders, said he woke up on Wednesday to a notification that Facebook had disabled the 157,000-member group. The notification, seen by Reuters, said without detail that the group violated policies on “adult sexual exploitation.” “We were first on the picking tree to be cut off because we are on Facebook, not a free platform like Reddit,” …