Why don't you just Google "uk man arrested for tweet" and you'll find plenty.
From the Verge[1]: Section 127 of the Communications Act makes it an offense to send public messages of a “grossly offensive or of an indecent, obscene or menacing character,”
Do I think threats are acceptable, no - and true threats aren't considered protected free speech. ("true threats first amendment" would be your search term, should you like to learn more)
Do I think offensive, nasty, hateful speech is free speech? Absolutely.
From the Verge[1]: Section 127 of the Communications Act makes it an offense to send public messages of a “grossly offensive or of an indecent, obscene or menacing character,”
[1] https://www.theverge.com/2022/2/7/22912054/uk-grossly-offens...