Comparing Corbyn's appeal to that of UKIP is false equivalency. A small but significant number of anti-Jewish conspiracy nuts have leeched onto Corbyn's Labour because they can use Labour's current anti-imperialist stance as a mask for anti-semitism, the racists and other bad'uns are on board with UKIP because racism and various other bigotries underpin UKIP's policy platform, or because people like Farage are happy to exploit bigotry to win votes. Whatever Labour's failings in getting shot of antisemites, and there have been some (for a start if I was in charge Livingstone would have been out as soon as he refused to apologise for his comments), it's not like Corbyn's/Labour's stance on Israel-Palestine are based in antisemitism, or that he's actively courting anti-semitism to gain votes.
Like many others, you're overestimating the 'fringe' nature of the bulk of Corbyn's support. 99% of them aren't the empty-cans-rattle-the-loudest strawmen you're envisioning, and that media outlets which tend towards both small-c conservatism and actual Conservatism like to portray them as.