Blame the parents.
Having worked in colleges and known quite a few teachers and lecturers in my time, I blame them. There's an old saying; 'Those who can do and those who can't teach'. Well in my experience all too often it could be; 'Those who can fit in with society in general and take a realistic and wide view of things do and those who can't teach'.
However, go back beyond their teachers and the parents back in the 60's were to blame. I was taught in the 50's & 60's by teachers who, if not fought in WWII, had been through it and they fostered open minds. Like sport, it wasn't the winning or losing of a discussion that was important, but the taking part - the learning of something new, the seeing of things from another person's viewpoint. After working in industry for any years, I went back to college to gain a qualification and was appalled at both the poor standard of the young students, but also the rigid dogmatic stance of many (but not all) of the lecturers. After qualifying I started working for two colleges and a charity that provided education for those who have 'slipped through the system'. Discussions with the college lecturers, whether informally in the Staff Room or formally in lecturers, was always a contest - one person or side had to win and the other lose - more like a political debate with a vote at the end of it - I'm right, you're wrong. On the other hand discussions informal and formal with students at the charity were a delight and warming to hear old and young, some of whom could hardly read and write more than their own name, putting forward well thought-out cogent arguments of their own views, allowing others to have theirs and saying at the end of it that they'd learned something, not smugly saying that they'd won or sneering because they hadn't.
When did education and intellectual skills stop being about the gaining and imparting of knowledge and understanding and start being a contest of enforcing opinions on others?