President Obama's press conference this week contained his testiest response yet toward “sanctimonious” ideological purists on the Left — the group of purists represented by the House Democrats who backed a non-binding party caucus vote against his tax plan in the House today.

I would not be the first to suggest that it could represent something of a triangulatory, Sister Souljah moment — a turning point for his presidency.

Obama's press shop famously brought down the liberals' house with its derogatory comments on the “professional left,” but the president's own previous dealings with the professional left have been a bit more cordial.

Here is Obama, showing a gentle side toward heckling gay activists at a fundraiser for Sen. Barbara Boxer, D-Calif.:

Here he is being heckled by AIDS activists in Connecticut, and showing a bit of anger (and giving an inaccurate response):