I'm old enough to remember the six-day war & aftermath very clearly. Israal was attacked by Jordan and had the right to defend itself. If a neighboring country attacks you from the territory they control you have the right to defend yourself. If they lose that territory in the ensuing battle - should you just give it back again so they should attack you again?? I followed the news & UN negotiations closely in 1967. The clear understanding was that Israel would return territories (not 'the' territories) captured in the fighting , based on a negotiated peace, with agreed upon borders. I remember clearly , an interview on TV with a defeated King Hussein who said that even he did not expect the borders to be the same as before the fighting began (& as was mentioned by another writer, these were armistice lines from 1949 - not true, recognized international borders.
Report in Lebanon: Israel Air Force strikes Syria's Quneitra, 3 terror operatives killed (Haaretz)
from the article: Israel's 10 worst errors of the decade