darren r,
I think as it is a live event, I am not sure that a full-blown conspiracy theory around HS2 has developed yet. However, some of the arguments around seem to have familiar traits. For example, I've spoken up as being in favour of the scheme - only to be accused of only holding that view because I must have some sort of vested interest.
It's an important debate, and we need to do many things to improve, upgrade and extend our infrastructure. Each option will be a balance of benefits and impacts, and so it is rightly a subject of discussion and variety of opinions. I am not saying that the situation is perfect, or that the pro-HS2 camp are always right about everything. However, it does not help when some on the anti-HS2 camp just make stuff up, selectively quote evidence out of context, don't answer questions, assume that as they don't understand how a railway works that their basic assumptions must be right, and so on and so forth.