Is it 'ethical'? As long as you're not talking 'Scientology Ethics'; sure
But it's also impractical and *very* dependent on how you do it.
1) The part of the 'Tech' that 'works' is the Mind Fuck, and yes, it's *designed* to reinforce itself at any sign of tampering.
2) The things that *might* work, such as forcible 'de-programming' are abhorent and usually illegal.
3) Under most circumstances direct 'attempts' to 'get people out' would be at the very least rude; almost always pointless; and always manipulative and socially objectionable. At the very least they give 'critics' a bad name, and, I'm glad that so few see that as their contribution.
From everything I've seen, Scientologists leave on their own timetable (almost all do,) for their own reasons (usually having to do with a 'Church' atrocity against them or theirs,) not because somebody 'got them out'.
The solution to Scientology is to prosecute the crimes committed in its name and the people committing those crimes.
Getting people 'out' is putting the cart before the horse; take the Cult away and it won't matter (much) who's 'still in'.
Zinj