They can be friendly enough in person until they figure out that you disagree with them politically. Then they display exactly the same behavior that they do on social media.

One guy I just happened to meet at my local pub when I was out with some friends and he was sitting with people that they knew, so we joined their table. This guy started talking politics right away and proclaimed his support for Antifa and punching Nazis. When I attempted to reason with him that you can't just physically attack people that you disagree with, he doubled down and proclaimed that anyone "preaching genocide" needed to be met with violence. That's just one example of a person I met in real life before I looked them up on social media.

My experience is that social media allows for a clear, unfiltered, and unfettered view into the true nature of a person. Meeting these people in person has only confirmed that for me. Most of the Democrats I know hate all Republicans and openly wish death upon them. Almost every Democrat that I follow on social media has hoped that the Chinese virus kills lots of Republicans. Several of them post death wishes and calls to violence on a daily basis.