It seems to me that the "let's demonize Robinson" (and the likes of Farage) plan has failed. It seems to me that whichever side you are on the first thing to acknowledge is that he has taken a lot of knocks and is standing proud and popular as ever, if not more so.
If your problem is that he's a deeply flawed individual with convictions and other unsavoury things in his past (and present?) then it's probably best to get over it. You don't like him, others do. Many (me) are somewhere in the middle.
If your problem is his beliefs then, IMHO, you have to first try your best to understand what they are exactly. Then you have a choice -
(1) Argue rationally why open borders and unlimited migration, including by young men who are often islamists (extremist by definition, different from other muslims), is a good thing.
Argue why a woman or child who was raped by an immigrant is no worse off than had the immigrant who raped her not come here. (You may regard that as me mis-framing the issue, but we are talking about convincing Robinson's supporters, and you have to deal with how they have framed the issue, not how you think the issue should be framed)
Argue why it is important that hurty words on twitter leads to prison sentences which can be longer than for rape or paedophilia
Argue that there is no risk whatsoever that Islamism will become more of an influence in the UK
Argue that "multicultural Britain" has been a resounding success in every way, and there is no need whatsoever for British patriots who believe in free speech and democracy and traditional "christian values" to try to forge a movement which tries to bring back a British national pride and unity based on something more than Blairism.
OR
(2) Take on board some of the above ideas into Labour or Tories or Lib Dems and try to ensure that by giving Robinson's supporters some of what they want we can avoid the likes of Reform getting power.
OR
(3) Ignore the "hard right" and Robinson and simply hope.
I think (3) is a bad idea. I think that the only option for Labour and Tories is to do both (1) and (2) simultaneously. Unless, especially in the case of labour, they believe that unlimited immigration, more Islamism (sharia law etc), smearing anyone with a union jack or st george's cross as racist, clamp-downs on free speech etc are hills worth dying on, and it is better to fight for what you believe in and lose to Reform, than give some ground and win to prevent the worst of Reform.
One more thing... it will be absolutely fascinating to see how the "new right" will pan out. We have Farage who many people on the right are sceptical of. Robinson who is very popular but has no party as far as I know. We have Rupert Lowe / Restore (a more intelligent and less grifter-ish version of Reform), Advance UK. It is possible that the right wing vote will be even more split at the next election than they were at the last... maybe labour can have a mini revival and end up with a big majority in 2029 based on 25% of the vote. Alternatively maybe it won't pan out because maybe Tories and Labour will start listening to people and the new right will be a trivial Reform and nothing else.