Well, from the personal intention standpoint, I don’t believe that anyone ever has the intention of going to a Mass to be schismatic and rebellious. Why? Because if a person doesn’t believe in the validity of the Pope or the authority of Rome, then how can they believe they are being schismatic? So while in our eyes and the church’s eyes they would be, they wouldn’t be in their own. In those cases, sure, it would be best not to do something that would lead away from the True Faith, but I sincerely doubt you’ll find any of those people posting here asking for direction on CAF.
As for the society as a whole, they are not schismatic, as I mentioned before. That individuals within the SSPX may be (whether some of the priests or those who attend) does not make a difference in that. There are individuals within the structure of Vatican II who are schismatic, too, but that, too, doesn’t speak for the whole. In my own situation, I’ll attend the SSPX (which I have done once) if it’s around and I need to get to Mass (I go to the TLM if I can), but I am careful about the people because I know that, as with any place, they are very mixed. Some people I would call crazy with their ideas and then there are many faithful Catholics, too.