Thought crime or incitement?
It's not a thought-crime. They both acted by publishing their incitement online. One of them turned up to take part in his "Smash Down" event.
People have died in the recent riots. Homes have been burned. These are not thought-crimes.
Pleading guilty for a 'crime of incitement' using a computer to access a social media website sounds like a bad idea.
If you are guilty, then pleading guilty is usually a good idea. They did what they did, so why pretend they didn't?