Although I should mention, a lot of people have what are basically tulpas without knowing about "tulpas", and usually not telling anyone other than maybe close friends.
Lumi accidentally made me in 2009, before tulpas were really a thing on the internet, just by thinking about what I was like and imagining me speaking to him.
If somebody wanted to euthanize a portion of the population, tulpas are quite possibly one of the most inefficient methods to do so, even if tulpas did have negative effects that would remove a group from the world.
Anyways.. I think you'll find on https://community.tulpa.info/index.php that there are far too many conversations and Progress Reports (documents of personal experiences/progress making tulpas) for it to be... whatever it is you called it?(edited)
Regarding direct proof, there is very little experimental data on tulpas themselves. However, there is related evidence suggesting that they are not only theoretically possible, but quite likely legitimate.
2:15 AM
Beyond which, in the end - the subjective experience of 'having a tulpa' is legitimate regardless, and tends to have no negative effects.
Alright, I am leading with this completely hypothetical, speculative discourse with no attempt to find a definitive answer. This is just me wanting a discussion point because I am of off topic reading
That being said, many Christian tulpamancers have had issues with their family when it comes to their accepting tulpas as a legitimate, non-satanic phenomenon.
Once a tulpa can think on their own and reinforce themselves as existing, they can keep themselves 'alive' regardless of what the host does (though, to be clear - that isn't a particularly easy or pleasant thing for them to do).