An Interesting Question

I just saw an interesting question posted in an online forum.

Why is Gafni / Degel Hatorah so angry about Shas joining the WZO.

When asked why Chareidim are allowed to join the Knesset, they usually answer that the Gedolim made a special exception, because of the need of the klal.

In other words, it really not allowed but the Gedolim permit it.

If so, Rav Ovadia Yosef, Shas's Gadol, allowed them to join the WZO, so what right do the Chareidim have to decry this move. They themselves do it.

(Indeed, within the Chareidi camp there are these that still decry joining the Knesset and publicly defame these who do.