>>>Zionism is a clear issur from the gemara (shalosh shavuos)
Even assuming that is true, what falls into the category of zionism/shalosh shavuos is certainly not a clear cut issue. Not in the Gemora and not in the Rishonim and not even mentioned in Rambam or Shulchan Aruch
>>>everything that anyone argues is a legitimate machlokes, no matter of the consensus of rabbonim etc.
The differences between what make someone a Rav or lhvdil a reform rabbi is not an issue of consensus at all. Do you know what it is?
In my experience people whose relationship to Torah and mitzvahs is so heavily influenced by their view on Zionism (pro or against)that it is a part of their identity usually are willing to bend Torah sources to fit their biases on the issue