It's not really about being 'close-minded' though, or 'less tolerant of challenging/controversial opinions than in the past' (tbh I'm struggling to see the distinction you're making there you might have to treat me like I'm thick) that's a conflation that morons like Sam Gyimah are making, but it mischaracterises the debate on campuses. It's more about the effectiveness of debating extremist rhetoric.
You might think that giving them a platform and ridiculing them is the best way to show up those views for what they are, but there's a fairly convincing argument that that is simply what they're after and the sort of vulnerable down and outers they're targeting will take the extremist message out of it and nothing else. People accept the orthodoxy of that view when it comes to extremist Islamic preaching (indeed, Universities are forced to deny those people platforms through prevent), but get squeamish when it gets applied to extremist right wing views. That's really all it comes down to, most people – as that poll shows – seem to accept that there's some topics where nothing gets gained from 'debate', it simply becomes a question of where you draw the line.