This sort of thing happen's round my way too. It's done by sad little people with no friends, who literally have nothing better to do. They don't care if you get injured either.
They get it wrong though. Making obstructions presents interesting challenges and in our woods, lots of new alternative trails appear. It can make a ride more intereting. They don't understand modern suspension systems.
If these eco-numpties really cared about their bit of woodland they would form a group of users representing each interest group. By working together, a sustainable compromise stands a chance of being reached and we could all live in harmony. They don't want to talk however, they want the place all for themselves.
All these self-righteous gonks are doing is causing damage and bad feeling. Themselves: ripping down healthy timber, disturbing habitat, pixxing off other legitimate countryside users (not just bikers). Bikers and other users: causing damage to habitat by making new trails to get around the obstructions that numpty has created.
It's nothing more than narrow minded intolerance. So that encourages me to specifically carry on using my chosen route to the contrary of their wishes.
If any eco-numpties who want it all their own way are reading this, come on, be big and let's talk!