People should be allowed to express opinions, even if stupid or offensive to some others, without looking over their shoulder.
In the case of the Bristol councillor, there were more appropriate remedies, like the Standards Board for England that could have been used. If this had happened in Parliament then the Speaker would have named the MP and suspended them from the house. That would have been proportionate.
The vociferous nature of minorities who feel themselves the subject of persecution should not lead to the law pandering to them just because they threaten acts of civil disobedience. More peaceful remedies than police investigation should be considered.
Oherwise free speech becomes that which is regulated by the Police.