When you are a member of a safe, advantaged group, and this choice is being made wholly voluntarily, I 100% agree (and am myself "childfree").
But telling a group that is under attack that they should not have kids is just furthering that group's diminishment. Once Israel isn't trying to wipe out Palestinians, and their survival isn't at stake, and they can make that choice without duress, then it's fair. Until then, this just seems to inherently create an argument that any group that is under threat should let itself die out rather than struggle on.
Why would you have them in the first place when they aren’t likely to have an enjoyable life?
Making a personal choice is one thing. Telling people that they shouldn't, based on their socioeconomic situation, is entirely another. "Survival of the wealthiest" is not an ideology I can conclude to be moral.