It's going to happen... people will gank you because...

A. You are a BIG target
B. They think you're a farmer or something
C. They think you are bots
D. They want a bigger e-peen by killing multiple lowbies at once
E. PVP == Gank... PVP != Fair Fight
F. All of the above

You can either...

A. Make a KOS list and just gank them everytime you see them
B. Go after all of their lowbies in their guilds with your 70
C. Red == Dead (keep rezzing and go after one toon over and over again... even if they get bored (because they out-level you) and about to leave you alone, go after them... eventually, they'll just want to leave you alone... but this takes about 30 mins to an hour or so...)
D. Peak hours, run instances
E. Level outside non-peak hours
F. When getting ganked twice in a row by the same people (or group), do something else for 10 mins and come back to it later
G. Try to get the hell out of that area (or zone) and do something else somewhere else.
H. Be on Mag server, horde side and call out of help from the calvary.
I. 2nd Set of toons at a lower/higher level to do something else