Since I am atheist I think it will be difficult for us to see eye to eye on this, but I will try to explain my perspective. This will be my last response though, because I'm not really interested in debating on this.
how do you know that the message of the posters is "and this is why you need to support the war?"
I am a media student, and one thing we are taught is that the creator's intent doesn't always matter, if the actual effect of the media is something different. So I can't definitively say that the people putting up the posters support the war, I've never met them, but that is the way I interpret them based on the social context that I do have. The reason I interpret them this way, is because of the political climate.
For example, there have been protests in my city in solidarity with palestine, calling for ceasefires and an end to the genocide, which have had counterprotests by zionist groups. If these groups don't support the war, I have no idea what they're protesting for. So when I see posters about the hostages, these are the groups and ideologies I immediately associate them with. Whether this is the intention or not I can't prove, but even if it isn't the intention it is the reality. Even if it wasn't their intention, the effect of these posters is to amplify the voices of zionism in my city, and what the voice of zionism is saying in my city is that palestinians should die.
would you approach either of the above questions differently if the posters had been put up by israelis living in diaspora? what if they had been put up by friends and family members of the hostages?
If the posters had been put up directly by friends and family of the hostages, I would feel a little differently. I would feel much less hostility towards them because it would be much clearer that the posters come from a place of love and grief. However I would still disagree with them, because of the reasons above (the intention does not change the effect).
If the posters had been put up by Israelis living in diaspora this wouldn't change my feeling toward them. Like I said in my first reblog: "their only connection to those people is their cultural or religious identity. To these people, the lives of the hostages are nothing but a symbol, and they are willing to support the deaths of fifty five thousand palestinians in the name of that symbol." Or, if you wanted to argue that they don't actually support the deaths of Palestinians, see my other point above: that's still the message they are sending.
how you would see actions like these? since these are things done within jewish spaces that the outside non-jewish world does not see or usually even know about, what do you believe is the purpose? are these also forms of propaganda? who is the audience?
I think this is the heart of where the ideological incompatibility is.
I'm sure that these practices are done with genuine love and care. I'm sure that it makes you feel a sense of genuine connection and kinship with the hostages. I can see how this would inform a lot of zionist's actions. But to me it doesn't excuse them in the slightest.
As someone on the outside, as I said above, I value human life above anything, and that means ALL human life. To me there is no difference between the value of an Israeli and a Palestinian. I don't want either of them to die. When you are practicing these traditions, you are placing higher value on the lives of the hostages who you have never met, than the palestinians who you have also never met, because of your religious and national identity.
I don't know if propaganda is the right word for this, because it seems like its less of a purposely constructed thing and more of an embedded cultural thing, but it still perpetuates an incredibly discriminatory bias, and your immersion in these practices is what makes you feel such a strong passion for the hostages. If you wanted to call it propaganda, then you are "the audience".
I wish I knew more about religious social systems to really unpack this, but thankfully this seems to be a bias specific to zionists and not judaism in general.
This is the last I'll respond on this topic, because I suspect my words will go to waste, but I hope you'll properly consider everything I've said, and I hope you can see why it's tone deaf to prioritise the israeli hostages when far more palestinians have been killed.