I think it's ridiculous and I'm struggling to get my head around the fact it's the output of the governing party of this country. I had to check, given the creepy music and black and white imagery are pretty much exactly what you'd do if you wanted to parody the Tories upcoming 'Corbyn eats children' campaign, but alas, that is the official account right there...
The video is ridiculous, but he does present a national security problem for the UK. He genuinely wants to leave NATO, which would present a threat to national security even with Trident. He wants to alienate the only superpower in the world and won't commit to a continued membership in the EU. If the EU were to collapse, which isn't likely but also isn't impossible, and the UK were out of NATO, it would present an additional national security problems as Europe fragmented back into nation-states without a common interest. It wouldn't be terribly surprising if he wanted to ally with Putin against the US/NATO because they've been ever so evil in accepting states into NATO that want to be protected from Russia.