The BBC doesn’t have the power to subject people to interview by force. If he declines an interview which he is not obligated to give what should they have done?
(a) not announce "interviewing all the leaders" until all the leaders were confirmed. This could be a competence rather than a bias issue; wasn't it Fyre Festival who were announcing acts who they hadn't booked to perform?
(b) empty-chair him
(c) given that Gove and Stanley Johnson (who has no formal position in the party, he's just Johnson's father and now a minor celebrity) turned up to protest outside, they should have been challenged instead
(also, "someone who already edits a partisan political magazine" should be disqualified from senior BBC positions if you're pretending to be impartial)
a) Various leaders agreed to go on a show. Boris Johnson doesn't have to go on the BBC and the BBC can interview who they wish. Andrew Neil likes to make fools of people on his show. He has done it to many politicians of all colours. It is really just a higher brow version of "Ben Shapiro defeats Liberals with facts and logic". Jeremy Corbyn was stupid enough to go on there and get himself shafted by Neil.
b and c) Gove and Stanley Johnson was sent by their party to the debate. Channel 4 (which is mostly publicly funded which most people don't know) did the whole ice sculpture as a stunt. They already bought the sculpture. The
As for the BBC having a "right wing bias". Nothing can be further from the truth. You can go on the website yourself and there are thousands of stories talking about typically left wing talking points.
I am actually building daily news site analysis tool by cobbling together some sources. I am using some fairly simple word analysis techniques (most of the effort is scraping the data from these sites and deciding what constitutes a real news story) and most of the language on the BBC and the Guardian are similar. I suspect that most of them just copy and paste stories tbh.
There is a more serious underlying problem you've spotted, which is "jounalism as stenography". Lots of people can put out press releases, which then really do get copy-pasted into articles. Same with "wire copy" sourced from AP or Reuters. This can be abused by bad actors to get obvious or difficult-to-refute falsehoods into the public memetic consciousness by repeating them.