Become a fan of h2g2
Think of your last trip to a Zoo. You see animals behaving themselves because they are given no alternative. Now imagine that society can also be seen as a type of Zoo. People behave in this "Zoo" because they have law and order imposed upon them. But some people in this society are predators. They are dangerous to their fellow humans. Yet they are placed in a box on wheels with the doors locked. At times this box on wheels goes into a tunnel. In the search for prey, these conditions are ideal for the predators.
These predators look for the vulnerable and the weak. They seek to do them emotional damage so that they can "feed" off the distress of others. Just like a tiger in a Zoo, they will rip your heart out if given the chance. The only defence against these predators is to show no fear. Indifference works best but you can also use pretend anger and open hostility. The trick is to convince the predator that you are not weak. Above all else you must never establish eye contact even for a moment. Turning your back on these predators is also a good tactic, if space permits you to do this in a cool and calculated way. If they speak to you pretend that you can not hear them. These predators can be bound with manners. Use social conventions to keep them away. But never be caught alone with them. They will attack if given the chance. Happy commuting.