Academia presents and explains ideas without value judgement.
That's impossible. Humans are subjective, and so values are always projected upon ideas. The best academia can manage is science, which still employs certain values to understand the world, but it at least attempts to maintain a relatively objective process.
If it appears that college educated people are more progressive leaning,
it's not because they were indoctrinated. A liberal education is in fact about the opposite of indoctrination.
College educated people are generally more liberal because they tend to be more intelligent.
Well, first, we should make a distinction between liberal and progressive. They're not the same. It's easier to suggest that educated people tend to lean more liberal throughout the world, but not necessarily more progressive. Progressivism is more of a specifically Western thing. Liberalism is Western in its heritage, but it has stood the test of time far better than progressivism.
Even so, educated people in many parts of the world outside of the West do not mostly lean more toward liberalism or progressivism. Conservatism is more the norm in much of Islamic academia, for example.
The world gets progressively more liberal over the arc of history..
That's not true either. Much of the Middle East was substantially more liberal in the early 1900s as compared with today. You could describe pre-Communist China as being more liberal than modern China in many respects as well.
The West becomes more liberal with time, but outside of the West, this is not necessarily the trend.
America get more liberal as well, but slower than more progressive nations.
We were among the very last to abolish slavery.
We'll be among the very last to have universal socialized medicine...but we definitely will have it eventually.
It depends on the issue and the region. America is much more liberal or progressive about immigration than most of Europe. America is conservative, overall, compared to Western and Northern Europe, but it is liberal/progressive compared to Eastern Europe.