You're allowing political rhetoric, mainly that he's Labour so better than the Tory option, to override the logical assumption that he'd be awful.
I'm not a Labour supporter to be fair, although nor am I a fan of the Tory government. Yet the thought of Corby in power really worries me.
Not because he's Labour or anything like that but rather he lives in bloody cloud-cuckoo land; him in power would be a short-lived catastrophe.
I think a Corbyn government on the whole would be better for the poor, sick and weakest amongst society, because he actually seems to have a shred of conscience about him
As you say, he's an idealist and I would probably not personally benefit from a Corbyn government, but I'm not benefiting under this Tory one either, so if I'm sodded either way, I might as well vote for the bloke whose going to help those worse off than me, rather than the woman who will keep stomping on them