Just because they're both stables of 3 people doesn't mean they have to feud. That's the same as saying two wrestlers should team up just because they're black.
Oh, stop. What about pairing two wrestlers together because they're white? Nobody ever brings that up. The whole point of the thread is to point out that we have two stables, and it would make sense for them to feud at this point especially since imo The Shield has gone extremely stale.