I totally agree with the essence of the argument but I don't think "identity" is the right word here. I think tribalism is what the author was getting at. Tribalism separates people into "us vs. them" kind of groupings and the more tribal minded someone is, the dumber he/she gets, as the author suggested. Religion and politics are only 2 forms of tribalism but there are others like sports, or nationality. Someone's identity definitely contains all these but as someone else pointed, there are non-tribal aspects of identity as well.