I can imagine GP is in quite a large group of those who dislike BA.
During my working years I flew a great deal with them. They had a comprehensive network, went via UK which suited my plans, and actually, years ago again, had a good product in Club World. I looked forward to the port and Stilton and a UK newspaper after a stint in some 3rd world shithole.
But then aggravation, from being messed about at LHR, trapped in planes that couldn't get to the gate, as time dripped away for the pain in the arse transfer from T1-T4 with rude slow security, being forced landside, so I had to repeat security there too, to dishonest treatment by them, lies lies and more over the years. Attempts to gouge me when changing routes/tickets and being treated less than decently where delays or missed connections occurred. They were on a downward slide then that they seemed oblivious to, with their arrogance and captive market in London.
Yes I hold a grudge, as does GP. Despite my last trip with them being fine, the shuttle from Manchester to LHR and back.
Although I flew to Thailand to start my retirement here on an air-miles ticket with BA, First Class, non-stop LHR to BKK one way, it was a flight I enjoyed. Of course it left late, BA 009 was consistent in that.