And that is each individuals own choice and I respect them for that. When it happens week in, week out then I'll agree with you but bare in mind that relatively few canx on MAN-LHR will be down to the "MAN gets chopped first". The majority will be your usual tech issues etc.
Also, you will notice that I said that it's a policy I agree with from an operational point of view. I don't expect your BA passenger to be happy about it, far from it. However, getting down to LHR by other means is much easier than from say NCE or MXP. When it's snow for example, the severity is normally localised making the trip South relatively easier. Once in LHR I would expect full assistance and flexibility from BA to get me where I was going from then on. Facilitating the movement of passengers under extreme circumstances (and the widespread shuttle cancellations tend to only happen in such scenarios) means that MAN is the obvious candidate to chop. If I was whoevers decision it was I'd make the same call. Similar difficult decisions are made by airlines world wide including EK, QR and EY.
I'm not 'sticking up for BA' regardless but your opinions do seem to be tinged with a stick two fingers up at BA for not operating at MAN sentiment. Of course that is an entirely different debate.