It has nothing to do with what he would say
It has to do with giving the dais (which would imply possibly an endorsement not of the person but what they represent)
This goes way back to Poland and probably further
It's a slippery slope to say that the Agudah needs to agree with every position of everyone who speaks on the dais. They let a board member of YU say kaddish!
My point was not to get into a debate over the hashkafa. My point was that if the speakers are preaching Achdus, but tailoring it to only a slice of the Torah community, the achdus talking points seem less sincere.
Maybe I'm misguided, but to me, the Ikkur of something like Daf Yomi is that so many people are learning the same Torah at the same time. I would never go to a standard Aguda asifa or meeting and complain about the hashkafa - I just thought the siyum was b'shitta supposed to be about achdus - which a large portion of it was - mostly the dancing and the actual siyum. The speeches around it (and the decisions of who gets to speak and who doesn't) seemed more to cater to Agudah's agenda than the overall siyum. And that's unfortunate to me. But obviously it's well within their purvue to run it how they want.