I would say if you 'teach' something with an attitude which says "This may not be disagreed with, altered or contradicted" and it CAN be disagreed with, altered or contradicted in some manner, then you're indoctrinating.
That SEEMS like a good definition but I'll bet there are counter examples that we would all agree need to happen, such as some values and behavioural things. Is it indoctrination?
I'm starting to think that indoctrination is either "teaching I don't like" or "teaching values that you should have a choice to adopt"
The 2nd one means - GUESS WHAT - we're in politics. They should, IMO, teach people that gay people EXIST. That isn't indoctrination, it's a fact. They should, IMO, teach people that gay people are people 'like any other' in that their orientation is not viewed prejudicially by the government.
If people want to teach their kids not to be gay, or eat fish on Fridays .... and teach it in the home then that's how it will happen.
"Be nice to the brown people" is actually a value that also should be taught, as civics. If we descend to tribalism, then our society (my city) is done for.