Why would you think that any left leaning person, or an MP would be involved in two men carrying knives?
It's nothing to do with Islam. Apparently it's a cultural tradition for Yemeni men. just like it's a tradition for Scottish men, when in traditional dress, but nothing to do with religion.
Currently only Sikhs and Scottish Highlanders are legally allowed to wear a knife as part of their culture.
It was probably an extreme right winger that turned up to the Henry Novak protest armed with an offensive weapon, his actions can't be blamed on all right wingers or politicians.