You're a good man, Jerry Brown—just not a good liberal. Being pro-abortion, according to the California governor, shouldn't be a prerequisite to membership or nomination in the Democratic Party.

"The fact that somebody believes today what most people believed 50 years ago should not be the basis for their exclusion," Brown said Sunday on "Meet the Press." "In America, we're not ideological. We're not like a Marxist party in 1910."

One Nebraska Democrat, a failed mayoral hopeful from Omaha, would disagree. This spring Heath Mello dared to run as a Democrat with a long pro-life record. And at the moment he was endorsed by Sen. Bernie Sanders, D-Vt., it even looked like he might win -- that is, until the party leadership decided to make an example of him because of his abortion heresy.

NARAL Pro-Choice America sneered that Mello's anti-abortion rhetoric was "politically stupid." Shamed into condemning the candidate, DNC Chairman Tom Perez admitted "every Democrat, like every American, should support a woman's right to make her own choices about her body." Mello subsequently lost by 6 points, and as he delivered his concession speech, some local Democrats angrily blamed Perez.

Brutal and merciless obedience to liberal ideology buried Mello. It was the political equivalent of shipping him off to Siberia.

Democrats like Brown hope to avoid that bloodletting. Both Rep. Nancy Pelosi, D-Calif., and Sen. Chuck Schumer, D-N.Y., have endorsed a bigger tent approach ahead of 2018. But that sudden political pragmatism can't overcome the loadstar of liberalism.

To just support abortion rights isn't enough. Since Roe, it's become everything. Even tolerating a difference of opinion is heresy. "Having access to abortion is ground zero for gender equality," NARAL President Ilyse Hogue explains. "It is linked to every other decision that women will ever make in their life." In short, there can be no middle ground inside the party.

While arguments for tolerance on the issue make political sense, they're an ideological non-starter. There's no way to unwind access to abortion with women's equality. And so, despite his good intentions, Brown can't be a good liberal so long as he strays from the party line.

Philip Wegmann is a commentary writer for the Washington Examiner.