He really is a bit of a plank isn't he ? He's called Nelson Mandela a terrorist and said that South Africa is now a hellhole after being an economic powerhouse. Is he really that thick ?

No, but he believes that we are thick enough to believe it.
Not a plank but a very nasty individual who surrounds himself with scary-looking knuckleheads.

He's not wrong on Mandela though, is he?

Statesman in his later years, but admits to giving the order to plant a bomb that resulted in the deaths of 11 people. I'd say that makes him a terrorist.

Or are "terrorists" only ever the bad guys we disagree with?

He's an ignorant knuckle dragging scrotum faced buffoon, his party is flailing to the point where most of his support comes from the even further right factions of EDL thugs, and people who think Nigel Farage is too posh to protect the working classes of Britain.

People constantly call for him to be banned from every social network, his party struck off the electoral commission, and booted thoroughly up the by Danny Tickle. But I think letting him have his say can only make him even less popular, same goes for the likes of the EDL. We don't even have to give them much rope for them to (figuratively) hang themselves with their constant hatred fuelled drivel.

'One man's terrorist' ... etc.

If Mandela was a terrorist, what about the apartheid regime that was entirely happy to shoot unarmed children?

Would resistance fighters in WWII have been terrorists too?

Absolutely agree. And the other aspect of that is that censoring them merely makes them martyrs.

A terrorist is a terrorist. Whether their cause is righteous, or justified, or not.

If you need to censor any "politician" in our first past the post electoral system then you are being undemocratic. No need to censor people unless you have PR.

Tricky question to answer, as the term is only used as a pejorative but the meaning of it is as you describe.

Unfortunately, the word is used as emotionally/politically as 'freedom fighter'.

Whether the cause is righteous, or justified, or not.

By which I think you mean that the BNP will get nowhere under FPTP but might get a seat or two under PR, therefore we'd need to silence his group to avoid a democratic result.

I don't think you've quite got the hang of this democracy lark.

Extremist parties can much more easily build support under PR. No "wasted" votes.