On my commute home today, a cabbie considerately gave way to me at Clapham Common, allowing me to cross the road. Unlike the Bentley driver yesterday who refused to give way despite him being in an almost stationary queue of traffic. I've heard many bad stories involving cab drivers and cyclists, but personally I've not had much cause for complaint. There are 28,000 London cabs and they make up the majority of daytime traffic in central London, so I'd be surprised if there weren't a sizeable number of incidents involving them. According to the CTC figures on crashes and near misses, only 6% of incidents involved a cab, which is about the same as buses or HGVs, and there are a lot fewer buses (about 7000 in London) and HGVs on the roads.
Of course there are bad cabbies. Take any population of 28,000 drivers and you'll find a sizeable number of bad apples.
I've long though that generalizations and prejudices do you little good. You start to mistrust and hate people before you know anything about them, and they tend to live up to your prejudices. You start looking for evidence to support your prejudices and before you know it you're a Daily Mail reader.