What's to object. My son is his own man .

If that was the result of thirty years of your nurture you may as well do nothing. You have not managed anything so far.

Since I lost the big V card 19 years ago, the fact my son invented time travel would be more impressive than him becoming a missionary.

Meh, his call and hopefully I'd done enough to teach him critical thinking and questioning it's not a totally harebrained scheme.

It's funny how many people who used to say my devotion and piety inspired them became atheists later. I wonder if it's contagious.

At thirty, that's their business. They would be an adult capable of making their own choices. I would be proud, because even though I may not agree with the ideology, it would be obvious that he has good intentions. I would also be excited that my child had the opportunity to travel to New places and learn about new cultures.

I would be profoundly sad and pity him for such a choice.

Object? Not really, it's his life and if he wishes to enter a delusional world of fantasy over facts, that is his choice. He may or may not recover from imaginary back to reality but life is terribly short and if he gathers a superior sense of holy servitude to an invisible sky daddy, for him, at this time, - - - if that's what he wants so be it.

Personally, I have a great deal of disdain for missionaries as they generally promote more societal damage then good.

Sorry for you loss.

First, his choice. Second. I personally got out of the act of analyzing/debating what religions believe. Its exhausting. My point is. If your son is doing positive things to legitimately help people thats great. To me beliefs and intentions are not indicators of quality. Its the actions of such persons. Trust me there are plenty of crabby free thinkers out there that can be even worse people ?

Not object at all. My eldest sing in Church on a Chorus every Sunday. My Children were Given to the World and to Life. I don't own them. It is their life just like my life was mine and not of my parents. I never been that Delusional!!!!

I would gently express my concern and support his decision. I would throw up later.

He's 30 yrs of age. His decision, not yours. ?

Make them read Chinua Achebe's 'Things Fall Apart.'

I don’t think parents have a right to “object” to a grown adult child’s decisions. You can be disappointed but they are able to make their own choices and explore their own beliefs at 30

No but I would be so disappointed.

I'd probably be so astounded I had a 30 year-old son that his choice of career would be a long way from my mind.

To be honest, I would encourage him to do so. I say this because doing things to help others is a good cause.
Myself, I volunteer at a homeless shelter. It's called Catholic Charities, so obviously it's a church run organization. But so what, Helping people is helping people.
And you never know. Just being around starving, suffering people in Africa, might just give him the push him into thinking twice about a 'Just' God.

Yes. Religion is a lot like a penis. I'm happy that you are so proud of yours, but if you start forcing it upon others, we gonna have a problem.

I absolutely would!
I'd also actively encourage him to GET away from that cult.
Perhaps to the point of deprogramming.