You don't need to ignore what he was saying, they are de jure Ukrainian waters, internationally and crucial according to the UK but it is important to remember that they are de facto Russian territorial waters and although they were sheepish in this particular interaction, they could be a bit more aggressive in the next one. This is not simple at all and the main point of my post was first to point out that saying they're are simply Ukrainian waters misrepresents the situation and is unhelpful and secondly, calling people shills when they provide useful nuance is just silly but he clearly did not get the message as he just keeps repeating that Crimean is de jure Ukrainian, which nobody is even disputing.
I am not sure what kind of a reply you are expecting from me, I've made my input at the begging of the thread. As I said previously I am not knowledge on the topic of shipping lane rights so I cannot provide any meaningful input in that regard although if somebody has knowledge regarding maritime law please share with us, I would be very interested to see whether according to the international/maritime law HMS Defender had to reply Russian coast guard when they demanded to alter their course or they were within their right to continue on their course without even acknowledging existence of the Russian coast guard (separate questions - one is if they had to alter their course when asked and if they have to reply the Russian coast guard - this question goes probably into recognition of Russian coast guard as Crimean, which is probably not straightforward and would go into occupational law, at least in de jure terms).
I was surprised HMS Defender wasn't rammed like the Russians did back in 1988 but I heard a US General/Official or something rather said that the reason the Russian coast guard did not do it was because they simply could not keep up with HMS Defender because the engine in their boats was supposed to be German before sanctions but because of sanctions they had to install Chinese engines that could not keep up with the UK warship, which is just hilarious. I wonder how true this is, it would make sense to take US official words regarding Russia with a pinch of salt though.
I'm sure they could slap a rocket on their boats to get the necessary speed.