During the Civil Rights era the Democratic Party consisted of two factions. The progressive northern/central component and the "Dixiecrats". These were southern Democrats who opposed Civil Rights and were generally much more conservative than the rest of the party.
It is the Dixiecrats that filibustered. The rest of the party put up with this because they didn't want to lose their majority. This was disgraceful, but is standard in the world of political expediency.
What has happened in the past 40 years is that those people who supported the Dixiecrats have migrated to the Republican Party. Which is why the south is now Republican and not Democratic.
So liberals were always conflicted over use of the filibuster. The issue is how to protect the rights of the minority. It is perhaps a little disingenuous of the Democrats now, but there seems to be little else they can do.
While it may be pleasant to gloat while your party is in control, it must be realized that the country is very closely split on most issues and that the control by a single party is more a function of the way election districts are drawn and winner-take-all voting.
So, if a party which has the support of about half of the populace pushes through a one-sided agenda we can expect some sort of reaction that they may not like. A better course of action would be to try and propose things which have the outlook of the majority party, but can be accepted by the minority.
Making an issue of a handful of judges is just bravado and will not lead to constructive legislation. There are plenty of other conservative judges that could be nominated without deliberately provoking a confrontation.
"Pride goeth before the fall"