On the day when a fascist terrorist who, other than his willingness to actually engage in violence rather than just talk about it, seems to have views not so different to those that have been expressed from time to time by various UKIP officials, is sent to prison for the heinous murder of an MP, one longs for the days when nationalists could simply be laughed at as vainglorious cranks.
In the Chinese-speaking world you see two particularly bizarre examples of this. The first is found in Taiwan where some on the fringes of the pro-independence movement take the whacky view that Taiwan is actually US territory. The logic of this is highly dubious - essentially that the US was the occupier of Taiwan post-war as the ROC troops who occupied the island acted under US commands, and as occupier the rights to the territory of Taiwan should have fallen to it after peace was made with Japan. Regardless of the validity of the argument, however, the real head-scratcher here is the idea that this advances Taiwanese independence - how the Taiwanese road to independence goes via converting Taiwan into a US colony against the wishes of both the Taiwanese and the US has never really been clear to me, but a very few on the pan-green side still seem to believe it quite fervently.
The second is one that I only heard of today: the idea that Hong Kong's New Territories were "stolen" by the PRC advocated by some on the Localist side in Hong Kong, including, apparently, Yau Wai-ching - she of Oathgate fame. Again, the logic here is dubious in the extreme - as expressed in the letter published in the Liberty Times (apparently published accidentally based on an early draft), the argument appears to be that the New Territories became part of the territory of Hong Kong as they were leased by the Qing Empire to the UK, and therefore the UK did not have the right to permanently transfer them to the PRC but instead the ROC should have inherited them. Again, quite how this argument helps the cause that Yau represents is not entirely clear.
Funny as the above are to think of, though, they do represent examples of the madness that lies at the heart of the nationalism now assailing many democratic (or, like Hong Kong, not-so-democratic) societies. People, once they buy into nationalism (taking here George Orwell's broad definition of the term) are willing to embrace the most facile nonsense so long as they understand that it is good for the "nation" with which they identify. Some Trump supporters believe that Obama was born in Kenya based on essentially no evidence. People in the Scottish nationalist movement have convinced themselves that MI5 rigged the independence referendum and is hiding Scotland's oil wealth. Pro-Brexit conspiracy theories were too numerous to count.
Whilst conspiracy theories like these have always abounded, modern social media seems to practically weaponise them and enable their dispersion far and wide, and occasionally people act on the extremism and suspicion they engender.