I think it is rather amusing that the United Kingdom is more concerned with preventing speakers the government dislikes from entering the country than with actual illegal immigrants who are an active danger to their country.
But I do not, in principle, have a problem with the idea that a country would want to ban entry to people whom it considers harmful to public order. In fact, I think they should do it more, and apply a stricter standard to those who are trying to stay there. If the UK did that, 75% of the political discord the leaders are worried about would go away, and having speakers arrive to bitch about how racist the country is (Piker, Uygur) or how it is being invaded (Tommy Robinson speakers) wouldn’t be a problem.