But there are counterexamples. The Scientific Revolution grew out of Christianity more gradually, and with somewhat less friction. Although the Church did try to fight back, the output of the scientists was simply too valuable to local populations and leaders to be suppressed.
Likewise, many countries saw royalty and nobility gradually be replaced by the burgeoisie in a non-violoent manner. The main exception, France, was a lot less successful in this.
Later on, while Marxism led to revolution in the Russian Empire, the labor movement in northern Europe decided to distance themselves from Marx, and instead work for the proletariat by reform rather than revolution. Not by attacking the burgeoisie, but rather by collaborating with it, and by leveraging capitalism to fund a welfare state.
But then again, neither the burgeoisie or the labor movement represented a fundamentally new ideology. Rather, they both adopted and adapted the ideology already in place, which was carredi by some combination of religion, scientism and patriotism/nationalism. The ideologies DID evolve, but in these cases, not in an abrupt manner, dictated by a few "intellectual" ideologes. And most importantly, they did not treat the pre-existing system as a mortal enemy.
History will show where the new ideologies will lead. At the momement, they seem to be very concerned with identifying enemies and not very interested in compromise. There seems to be more appetetite for conflict than the world has seen since the 1930's, and it may be wise to prepare for some kind of rupture within the next 5-30 years.
That just means they got told about socialism/Marxism by some other authority figure besides their parents. I never said that parents were the only ones that could tell people such beliefs and have them accepted and made part of the person's identity.
> I suspect gravitating towards an ideology is often as much motivated by what you are against as it is motivated by what you are for.
This can quite often explain why people accept beliefs by being told them and making them part of their identity, instead of considering and weighing evidence, yes.
I've come across countless counter-examples to this in my life. A lot of the socialists/Marxists I've known come from relatively well of conservative families for example.
I've no real evidence for this except personal anecdotes, but I suspect gravitating towards an ideology is often as much motivated by what you are against as it is motivated by what you are for. If there's a hierarchy in power, political, religious, whatever, that you think is corrupt you're going to naturally gravitate towards an ideology that provides a narrative as to why it is corrupt and what can be done about it.
People fed up with corruption in catholicism gravitated to protestantism. People fed up with feudal or capitalist hierarchies gravitate towards Marxism. People in the Muslim world fed up with the economic and military domination of the West gravitate towards islamic fundamentalism. People fed up with Communist totalitarianism gravitate towards democracy. These counter-narratives provide a framework for opposition and an agenda that opposition can rally around and unify on.