Some of the "hate" comes from BA used to be a world class, innovative airline. As an example they introduced the first lie flat beds 20 years ago. For perhaps the last 10 years or so, they have rested on their laurels and in the last couple of years aggressively penny pinched the product and service. If I recall, the standard for wines in First is nothing to cost more than 5 Euro per bottle (champagne excepted). It wasn't that way 15 years ago.
It's become a shadow of it's former self, and it's sad for those who knew and loved the old BA to see things quickly descending into mediocrity and low cost carrier levels of "service". It's like watching an old friend slowly die before your eyes; yet you know it doesn't have to be this way.