Don’t larger military alliance disincentivize violent conflict?

Not necessarily - and NATO sure doesn't seem to mind when their own members wage genocidal wars on the third world (like Turkey is doing with it's ISIS-staffed proxy-militias in northern Syria).

NATO has shown that it will happily play midwife to US neocolonialism - remember that time the US invaded Afghanistan using an even flimsier pretext than the ones Putin uses? At this point, we should be thankful that the US didn't allow Russia itself to join NATO (something Putin is still pretty sore about)... but the US sure didn't do it out of the goodness of their hearts.