Punch up not down. Democrat leadership decides on policy, Democrat leadership decides on election strategy.
"I won't vote for leader that heinous thing x" is a reasonable position to have. "I will vote for leader that doesn't heinous thing y" is also a reasonable position to have.
The compromise isn't to get people to vote for x, it's for the leader to stop x. Particularly, if the opponent would do x but worse. That only shows, to the Democrat leader, y is a resonable cost for x.