The Bushie case is a sad one, but to be fair, what other option did the farmer have? If we're going to ban tasers, then the state itself is at least partly responsible for his death.
Even if tasers were legal, I'd still defend the farmer's right to use a firearm. Maybe he still wouldn't own a taser or couldn't find it or had't charged it at the time or feared the intruder had a firearm that could reach further than a taser could, or he just doesn't trust the reliability of tasers, etc.
However, by making it easier for a person to buy a taser, we'd be increasing at least somewhat the probability he could opt for a taser instead of a firearm.
A friend of mine was once robbed at knifepoint. A taser might be no match for a firearm but it might equalize a fight against a knife.