We like to think in easily separate-able categories, black and white stuff (absolutely no pun on race in this case). We are also able to hold opposing viewpoints in our heads at the same time. And we are all susceptible to political messaging. It's like advertising; it wears people down.
So you can be a true believer of whatever Christian church and support a man in the White House who couldn't be much more from your professed ideals if he tried. You can also think abortion is murder and support killing children in Iran. You can believe in civil rights and still want no Arab looking neighbors. We are full of contradictions.
The US suffers also from only having one more mainline party than North Korea or the PRC. If you look at other countries that are democracies, you'll find half a dozen parties vying for power. It offers more tents to assemble under, whereas in the US most people end up under one of two and arrange themselves with the inconsistencies between their own values and those of the party consensus more easily than in France, just as one example, where Macron launched his own new party before he became president. (Just for balance: 2+ party democracies can also still be shit at the end of the day but they offer more choices.)
No, people would not. It could be a tool for moderators to curb spamming but I don't see that being more effective than existing moderation tools.