Here's a good video debunking Packham's lies about HS2, the assertion that it wasn't designed by railway experts is a new one to me and is pretty absurd. I fully agree with transitioning away from oil and we need a massive increase in rail capacity (HS2) so we can stop driving so much. To me, straight up opposing HS2 is against his environmental aims and Packham's use of misinformation on HS2 hurts his credibility.
How does supporting Just Stop Oil not help his cause? They seem like they would be right up his street.
The only problem with Just Stop Oil is that they are like PETA, in that they are too extreme for people to join in with, but fundamentally they aren't wrong and help shift the Overton Window.
Their actions drive more people away from their cause, rather than encouraging more support. Surely that's the opposite of what you want if your aim is to achieve change.
Annoying ordinary people is not going to get you very far.