Running away is never the solution to any problem, i know many a tale where this has happened i.e one set of parents is dead against the union, often prompting the other side to feel the same.
many of those cases have been resolved when the party wanting to get married have stuck to thier wishes and convinced the parents to agree, may seem like an uphill task, but there are ways around it.
He needs to do a lot of work in convincing his mother and getting her on his side, you run away and get married, this "scar" will remain with you forever, you will always be know as the "one that ran away".
No parent deserve this kind of humiliation, your B/f needs to change the course of action if he really wants to spend the rest of his life with you.