The way you ask this makes me think you are a troll that wants to pick a fight.
Just in case you are not a troll: "vegan defenders" and "vegans" are no homogenous groups. There are a lot of different individuals that are vegan. And they do this for a bunch of different reasons.
Also your "vegan defenders": Defending against what? This implies that there are people who think veganism should be eradicated. This would be an extremly stupid opinion to have. You don't have to be vegan yourself but at least let other people live their life.
The problem is that you assume this is a normal train behavior. It is not.
If your question is truly about the general efficency. here is the very first article that i found https://www.thegreenshot.io/uncategorized/train-vs-car/
But all your answers make it clear that you don't care about your question, instead you want to complain. And rightly so! This is shitty
Just stop fraiming it as if you are asking a question. It is not happening with well designed infratructure and is not a general problem with trains.
Maybe in your specific place it might even has a net negative impact. But almost everywhere else trains are saving tons of fuel.