Bartlett never said that. I suspect he is angry that the conservatives DO NOT ACCEPT THE BIG TENT AND DO NOT ACCEPT THE IDEA OF A CENTER RIGHT COALITION.
The GOP is in trouble because it opened up the party to people who do not share its core values. That was the "Big Tent" that included a Welcome, Amigo! immigration policy, a more "even-handed" approach to the Middle East (moral equivalence between Israel and Hamas, except Bruce likes Hamas better), acceptance of a huge Federal Government, gargantuan Federal spending along with a new prescription drug entitlement program, and acceptance of abortion as just a "lifestyle choice".
Thanks, but no thanks. That's not America's center: it's Washington and New York's idea of America's center.
The Reagan coalition - a center-right coalition - lies considerably to the right of where the GOP is today. In order to get back there, which is to say if the Republican Party ever wants to be relevant again: they need to promote a clearly-defined set of principles.
Then they can welcome new members who discover they agree, welcome back those who left in disgust (like me), and let those go who cannot agree with them, like the esteemed Mr. Bartlett, who I think would be much more comfortable with the Lew Rockwell Brigade.