You asked “How is that any different than the Republicans doing this now?” That’s the difference.
Merrick should have gotten a hearing, but he’s far from the first to have his nomination halted for purely political reasons. I’m sure we could throw examples dating back to Reagan for this. Democrats say conservative judges are picked, Republicans say too liberal/not conservative enough judges are, or the BS about an election year. Obama was in a unique position for nominees being obstructed, unfortunately. Neither party is innocent, though.