There are 134 FBS programs. Only 34 of them are in the B1G/SEC. They want to exclude teams, fine. Be excluded.
If the other 100 FBS programs refuse to play them, let them beat each other up in the regular season. They can't claim conference superiority if they never play anyone outside their two conferences and their one-off FCS games. Then, to drive this point home (and, yes, I get that there are 300+ D-1 basketball programs) refuse to play the B1G/SEC in both MBB and WBB.
The B1G/SEC (and just like in politics) and the media (looking at you ESPN and Fox) will wake up and figure out that CFB ≠ NFL/NBA and that there is a large chunk of fans that will turn off the B1G/SEC when they only play against themselves.