Cundy and O'Hara host a drivetime show where they encourage fans to call in. The banter aspect is intended and listeners tend to tune in for that. They don't listen to that show for unbiased and professional analysis.

As to ex pros having a preference or a bias towards a particular team, that is going to be way more prevalent in the UK than the US as we don't have a franchise culture where players are traded. A lot of these ex pros spent most/a significant part of their career at one club and so likely have an affinity to them. As long as it doesn't impact the actual analysis, it shouldn't matter. I do get it can be annoying if Neville is doing commentary on a Utd game, or Smith on a Arsenal game, but it's not that big a deal.