The first lynchings were when the frontier lacked any law enforcement at all, and groups formed to go out and kill the people committing heinous repetitive crimes.

You must realize that lynchings were capable of spinning out if control, but many of them were completely valid as well. The last lynching in iowa was of a weapthy guy who killed his 3rd wife and stepson in front of several people. Several rich people had done similar acts and basically bought their way out of jail, this was the townspeople put a definitive "if you're rich and killing people we will end you and your money won't help" moment.

That may be a factor in why they're so fanatical about pushing the "lynchings bad" narrative.