You are right in that we share a city with them, Danny Boy. You are right that we both have a varied set of supporters and even they have the odd one with some level of intelligence.
BUT........
When it comes to talking SWFC, to a man they are among the most deluded people you could stumble across. I know and have known loads of them down the years and yes, some of them come across as intelligent, level headed and reasonable people but mention of SWFC removes any semblance of the aforesaid. They actually believe they are a "MASSIVE" club, remember the "big six"? Yet when you confront them with the facts, their eyes glaze over and their brains turn to mush. When you point out they haven't averaged 30k since 1967, they don't believe you. When you state that United have done this twice since then despite having a much lower capacity stadium, they are struck dumb. When you point out their sub 11k average in the mid '70's they enter a state of denial akin to Hitler in his bunker. When you point out that average crowds between the 2 clubs is there or thereabouts within 2k over the course of history to them, they shout you down. Their attitude towards other clubs is one of arrogance, disdain and disrespect, "tinpot" being a favourite description.
Remember Lee Strafford? He claimed a potential 500k fans in the UK and 4 to 5 million across the world! They believed him, they genuinely did!!
And to address your final point regarding "floating" support, you've got to remember that Hillsborough provides facility for one of the largest away followings in the country. The 34k crowds you quote more often than not contain huge away support. Again, when you provide this information to an owl, they look to the skies in disbelief and emit a low humming sound.
The list goes on and on regarding their delusions. Yes, they may look the same as us, work with us, live next door and even be related to us. But to state that there is "absolutely no difference between United and Wednesday fans" is just not true.
Thankfully!