It's Russia's purpose to attack its peaceful, friendly and neutral neighbors.

No one forces Russia to attack its neighbors.

As long as Russia insists on waging war against its sovereign neighbors, Russia is a threat to Europe.

you put your life on the line now, or you put everyone's on the line, later.

WW2 didn't have to happen, and the UK and France could have interviened sooner, before the Nazi war machine took over the Czechs, the Poles, etc.

ounce of prevention vs. a pound of cure

Did you read what he said? You are guaranteeing the war will continue if you reward an invasion with land.

It's just lie. If, for example, NATO gives clear guarantees to join in for Ukraine in the case of next attack(if any agreement on ending the war is reached), then there will definitely not be a next attack.

It's not a lie. It's exactly the same reason you don't let a burglar keep the stolen goods.

NATO does not even consider applicants in the middle of conflicts or even with disputed borders.

According to your theoretical, Russia could attack and immediately invalidate Ukraine's ability to join NATO by re-triggering a conflict.

Come on is this stuff really that hard?