I'm convinced that she's in earnest about her art, and is really working at it simply for art's sake and not from any selfish motives.

Therefore, as an educated man, it's my duty to help her if I can, without outraging my own conscience or acting in any way unsuitable for a clergyman.

Assuming Simpkins to be the kind of man you describe, it is a public duty, the duty of every good citizen, to put him out of the world altogether.

He's nothing but a nuisance here, and he can't be really happy.

I imagine that even for his own sake he'd be a great deal better dead.