the bbc is world renowned for its neutrality , have a look at news tv in america for mental partisanship... its not ever going to be perfect but if u think its for the left remember the treatment they gave diane abbot on question time.
The BBC are without doubt biased towards remaining.
And as for the treatment of Dianne Abbott, I watched that episode and there was nothing worse done to her than to anyone else on that show. The fact is that’s she’s a proper, massive idiot and couldn’t give s coherent answer to anything asked of her and was called out for it. Nothing more. Maybe she’d have done better had she stopped thinking about her next jump on old man Steptoe?