KiwiPundit is getting a little hysterical about Helen Clark here, but his basic point is sound. David Irving is being denied entry to the country on the basis of his views. While his deportation from Canada is the pretext, it is ultimately based on his conviction for Holocaust-denial in Germany. Our refusing entry on the basis of that deportation is an implicit endorsement of Germany's restrictions on free speech. That's not something a country which claims to take human rights and freedom of speech seriously should be doing.
It would help if Irving wasn't a Holocaust-denier, and it would help if he wasn't such a self-important arsehole who likes to play silly-buggers with immigration authorities (as he did in Canada, and as he seems to be trying to do here), but there's an important principle at stake. Freedom of speech is not there to protect popular people or views. If we take it seriously, we should ignore Irving's deportation as being based on a violation of his human rights, and allow him to enter. Then, we should take the opportunity to let him and the world know exactly how much we disagree with his views.