Meanwhile ignoring the actually violent far right to the point that we had arson attacks in Belfast and a stabbing spree killer in Edinburgh.
Not to argue against the point you're making but these aren't good examples. Policing in both Northern Ireland and Scotland are fully devolved and operate independently of the government in Westminster.
This is orthogonal with how police should tackle the violence you mention.
Edit in response to @pjc50's replay below:
The signs are a serious criminal offence. Supporting a proscribed terror organisation is a serious criminal offence according to the law and arrest is unavoidable.
Edit 2: What constitutes a "serious criminal offence" is not subjective based on one's personal opinion, it is what the law defines as such...
The police always have a choice as to which crimes they investigate. This is why petty theft in London is almost totally ignored.
(and the underlying decision to proscribe Palestine action was, of course, taken by Keir Starmer. It is a significant part of why he is out now.)
(edit war: "the signs are a serious criminal offence" -- this is why the Americans will be laughing at us about freedom of speech when they wake up on this forum.)
I don't see corresponding arrests being deployed against Twitter posters who were supporting the riots in Belfast, including the firebombing of immigrant homes, for example. I guess that's because they're not an organisation with a name, which is the important thing, rather than the actual violence?
This was literally a decision Starmer personally made, to put Palestine Action on the proscribed organization list. Without that the signs would not be an offence.