Google "bbc bias against labour".
The New Statesman, the Indy, and the Guardian seem to agree the that BBC (and other media) have given Corbyn and the labour party a bad time.
Now Google "bbc left-wing bias"
The Daily Mail and the Express run with this one. Oh and the Independent...hang on...
Basically if you think the BBC has a bias against your personal political leanings, you will find "evidence" (mainly in the tabloids and social media) to support your assertion...no matter what your political leanings actually are. In the same way as you will find evidence to support your view that the Moon Landings never happened, that JFK was killed by the Mob/CIA/FBI/Oswald, that the World is flat, and that the British Royal Family are all lizards.