When I talk about it as an exertion of will, I do not mean strength or willpower. When I say will, I mean agency or choice. I somewhat agree that killing yourself is far more simple than grinding on with a life you have no interest in living, but I think a person has a right to decide what they do to their own body--even to the point of death. I'm not trying to say that anyone should kill themselves over living... I am saying that they have a right to and it shouldn't be deemed selfish or weak. I believe the entire issue is a matter of bodily agency. 

It also has very little to do with happiness and everything to do with stability. I think I agree with Schopenhauer's views on the Freudian Death Drive, which basically says that there is far more suffering in life than happiness. So what would counteract a lack of happiness and make life worth living in spite of all the suffering? Stability. It's a natural craving much more achievable than constant happiness, It's a security blanket which we can hide behind when things become far too real. Anything that shakes our stability forces us to look at the Real instead of the Virtual or ideological... Which can be quite unpleasant. After all, who wants to be reminded of trauma instead of the comforts of habit and ignorance? I hope I didn't grossly oversimplify Freud and Lacan there, and that you get my point.

Suicide is the final attempt at stability. After all, what could be more permanent and consistent than death? I don't think that killing oneself is the best choice, and I would never recommend it to anyone, Yet, given proper circumstance and consideration, it could serve to end the suffering of that person. The counterargument to this is, of course, that suicide disrupts the stability of those around the victim. I think this effect would be significantly lessened if there wasn't such a stigma behind suicide, so that it could be discussed with friends and family in a way that the concerns of the victim and others are brought to light. ...But perhaps this is too ideal.

I guess, then, even if the victim is a whiny twerp killing themselves to spite those they feel wronged by (which I highly doubt many suicides are like), it's their body and their choice.