The problem is not that a whole generations are either good or bad but that a small swing in attitudes make the group as a whole either likely or unlikely to indulge in this sort of intolerable anti-social behaviour. For whatever reason, the experience of most is that attitudes as a whole have deteriorated over time, and one can only look to see what we, as a society, are getting wrong.
Certainly the increase of individual self importance has not helped. To create a good society one needs to be taught the balance between one's rights as an individual and one's duty to the rest of the public. And that seems to be on a downward spiral.
Once, many would agree, discipline was too strict, resulting in pupils being hit with rulers or other physical punishment for minor things, such as blotting your exercise book. But one can not help but think the desire to correct that has sent the pendulum swinging too far. Even if trying to understand the difficult pupils works, we don't have the resources to pussyfoot around, and there is always the danger that if you tried it would be seen that those who play up get given all the attention/advantages. Society needs general systems applicable to all, that achieves the respect citizens need.
But to go back to the main point, it isn't so much liberalism is wrong and intolerance right, its is about knowing where the balance is such that one gets what
I don't think it is likely to discover a system whereby each individual is treated perfectly to achieve the best, practical considerations mean there will always be something to complain of. But surely we can do better than we presently are.