Now that's a statement. I'd take issue with it even if it stated the opposite. I've played excellent solid state and tube amps and crappy solid state and tube amps. I don't think an Ampeg SVT (though I own and play one) is the be- and end-all of bassdom. It does some things better than my Ashdown and Markbass rigs and some things worse. I like the treble and the mid range of a tube amp (though treble will never snarl like it does on a solid state if that is what you are after, I'm not), but I think as regards bass and sub-bass
most solid state amps project things more tightly and accurately than
most tube amps (certainly both my Ashdown and my Markbass rig reach frequencies that the SVT has given up on, whether you need these frequencies is a matter of taste); with a tube amp low bass tends to be everywhere and not very concrete, which feels nice for the bassist, but causes issues for the mix. There is a reason why the 8x10 fridge that goes with the SVT is no sub-bass wonder (I've added a 1x18 Ampeg cab to mine for that reason), it camouflages where the SVT loses accuracy, not that that is an issue in most playing situations.
Am I in a minority and do you actually have to be religious about playing tube or solid state?