I think when people say that someone is 'lecturing' they mean 'someone I don't like is giving their opinion'. It sounds childish to say that someone is lecturing. As if you see them like your unpopular headmaster.
Someone we don't know and who we may or may not like is giving their completely unqualified opinion, to which they have every right, but no more right than you or I or any other unqualified person. The only thing getting them the airtime for that opinion is their unearned privilege, and that privilege is maintained by us paying for him to sit in a mansion, do what he likes and tell us how to behave while doing the complete opposite.
A headmaster, however unpopular, may at least be qualified to hold that position and have some authority.
PW is a taxpayer-subsidised ex-helicopter pilot desperately trying to justify his family's existence with good causes.