If you are ever asked this question, or any variation of it, by someone who supports Israel, do not dignify it with an answer.
It is nothing but an attempt to distract from the obvious fact that for the best part of a century the Palestinian people have been living under the boot of an oppressive apartheid regime that is guilty of crimes that far exceed anything Hamas could ever even dream of committing.
Do not give the zionist fucks an inch.
As far as I understand it, for a post to appear on your instances all feed, someone from your instance needs to have subscribed to the community on the other instance that the post is from.