Define sin first. Killing yourself results in death. Religious fanatics stretch definition of sin to whatever they don’t like.
Gays? Sin? Woman without hijab? Sin. Abortion? Sin.
> In my view it's the same: You are limiting someone else's liberty; forcing them not to do something you consider a grave mistake.
No, it’s totally not the same. And it’s not necessarily about mistake. Allowing people to commit unrestricted suicide would set a dangerous precedent. And on top of that a lot of inconvenience for people around.