If you can't earn votes because another democrat is in the race, then you don't deserve votes. Warnock looks like just another lazy bum who wants to bully people so he doesn't have to campaign, just like all the rest of the establishment-endorsed lazy bums running for office this year, like McGrath. I haven't been following this contest too closely, but
his wikipedia page says he's endorsed by Gillibrand, Corey Booker, the SDCC, and Obama which means that Warnock will be an opponent of medicare for all. If you can't get behind medicare for all, you don't get my support.
Liberman does not have that problem.
So he's just another lazy bum, in politics more to fleece donors than to change anything, so Warnock doesn't deserve a senate seat. Liberman is doing the right thing to not let Warnock bully him. We need more progressives to stand up to assholes like Warnock.
If you really are concerned about winning so much, though, then why doesn't Warnock leave so LIberman can win? Spoiler theory cuts both ways.