Anybody who does not hear diffrences between a SET amp (any one) and any class A or AB solid-state amp is either
Well the only reason that you may hear a difference is that one has distortion or coloration that the other does not (for example at higher output levels or under certain loads) or alternatively you "perceive" a difference when you know what you are listening too. Fundamentally there is absolutely no reason why the two should not sound the same (given the right designs). I don't doubt that you may have come to believe you can hear a difference, after all a typical high quality tube amp output transformer will behave like an EQ when connected to a variable load such as a speaker and this change in coloration is indeed audible (it is like a mild form of tone control which follows the impedance curve of the speaker - very slight and in no way detracts from the sound - but certainly audible in most cases).
BTW - I have nothing - absolutely nothing against tubes - they can and do sound fantastic - they are awesome and hands down beat SS amps for producing a warm sound to music which is rich in even harmonics and the way they clip makes them absolutely essential for guitar amps and some microphone applications.
However, claims that any old tube amp is better than ALL SS amps is just wishful thinking. I commend your enthusiasm - tubes rock - it is nice to have total conviction - it simplifies your choices and allows you to snear at anyone so stupid as to use solid state amps!