DO “Both Parties Do It?”

Really? Both parties do it?
ANOTHER ANGEL LOSES ITS WINGS…. ,

In a column devoted to highlighting Republican extremism, the Post writer just had to say, “Both parties have been undergoing ideological cleansing.” The observation was both wrong and superfluous.

What examples show “both parties” do it? Pennsylvania, where a Democrat is running in a primary against a Republican who switched in order to “get votes.” Apparently it is extremism to run an actual Democrat in a Democratic Party primary.
And Arkansas, where Lincoln has taken tons of cash from corporate interests and blocked the President’s agenda, and the Chamber of Commerce and other Republican groups are running ads for her.