[Mitchell's Navy]

I think the opposing argument would be that the future was already changed so much. Wes was originally supposed to take over for his deceased father. Than Alex made his father live and Wes remain a Ranger. So history changed to Wes dying to defeat Frax and Ransik, Then in the end the future changed to the Wes surviving. So it makes it plausible that Wes would be able to leave for the future without damaging it.