I think the rebbe tried to parse things. So there is the belief of zionisim and then there is the idea of supporting Israel and even more so not making peace with people bent on killing us.
The rebbe was very famous for giving a sicha after the yom kippur war when israel was a couple of hours away from Damsucus but stopped short of capturing it and accepted a ceasefire because of UN pressure. The rebbe said “der UN vet shrien si vsi velin zi shrein a bissel hiecher” (The UN will yell anyhow so now they will yell a little louder).
The rebbe was also very famously against Oslo or any pace deal. Contrast that to R Shach z’l who was pro Oslo. The rebbe was pro living in settlements too.
All In all the rebbe took a very anti Palestinian view. But he still held that fundamentally the state of Israel is a bad thing in ideology. Its kind of like now that its here even though we don’t agree with its principals, its still jews and we need to keep it safe via fighting and being anti peace with people who are ina cult bent on killing us no matter what. A fake peace. i wonder what he would hold today of the flag. The flag histrocially represented the ideals of the state which is bad. But nowadays its intended to represent a more general symbol representing the jewish people and its existence against the Palestinians and musilm enemies around the world who seek to destroy us. it isn’t really about the ideals of zionism any more. (Kind of post zionism). I suspect the reba would be torn about the flag now and i wouldn’t mock shluchim that used it. You can’t bring a proof form sichah in 1955.