Re: BBC
no other media outlet needs to do this
Not strictly true - or at least, I believe it not to be, yet. Print media is different but broadcast media has always had a legal requirement to be "balanced", so much so that at election time there is a formula regarding how much air time each party is allowed. When I worked in local commercial radio we essentially had people with stopwatches timing everything and totting it up to make sure we stuck to the formula. It's based on the amount of support they had in previous elections so there's a bit of chicken-and-egg going on, but the principle is sound.
It works (or used to work) reasonably well, and is the reason that in some elections even the disappearingly small parties such as the Monster Raving Loonies are invited onto discussion programmes and have their manifesto launches covered in news bulletins. Something similar is applied to Party Election Broadcasts so even the small parties get to make one or more Party Election Broadcasts.
Note to non-UK readers, commercial broadcast advertising by political parties is banned in the UK, and there are strict rules about party funding too*, though as always there are loopholes.
M.
*Every time there's a presidential election in the US, I wonder if they'd benefit from rules similar to ours governing funding, advertising and the length of the actual "campaign" part of the election. It seems to mean that the barriers to small parties entering local and national elections in the UK are significantly lower than in the US (particularly the funding). I have no experience, but I believe similar, possibly better, rules are in place in other countries too.
Imagine if there was a truly national third or fourth candidate in US presidential elections, backed by a truly national third or fourth political party...