It's pretty tough to reliably stop/disable somebody without at least a risk of killing them. Tasers still kill people every now and then, and their effectiveness is low enough that police usually only use them against unarmed people or with lots of backup armed with lethal weapons.

There is a trade-off, there, however. Someone is more likely to use a non-lethal weapon than a lethal one, including police, etc - but non-lethal weapons are still very intimidating.

With enough non-lethal weapons, it might make abuse of government power more likely, not less - training mace sprays and tazers on protesters is more acceptable than just mowing them down with bullets, but disperses crowds just as well.