They can and they should if they want to. There’s even now a place to do it and no one can say it’s out of order there. I wouldn’t even put McD’s out of bounds. Some of us find things to like there and McD’s especially is reported to be changing enough that more likeable things could be coming. In the past, I posted in praise of the McD’s $1 double cheeseburger (now $1.39 in SF–who says there’s no inflation?).
Personally, I’m for free speech. The only thing I would put out of bounds is personal attacks, egregious profanity or other offensiveness for no obvious good reason. But we have moderators to make these decisions and they have NEVER said that discussion of chains was verboten.
So I say, "Discuss away" and I promise to help defend you, though I may also disagree with your opinion, if you are attacked for doing it. I hope some more of you will promise, at least to yourself, to speak up in such a case as well.