the voltage between the emmiter and the base is around 4v in tip122 (+/- .5v depending on the driving conditions)
based on this piece of information, you can see your shcematic, calculate and discover that the base voltage on the upper transistors is the not the same on the lower transisors(atually lower transistors have vrey low base voltage, about 1v)
So the 10K resisotrs are just to mantain the same current on the base's of the 4 transistors.
Also, No you don't need protecion diodes, the TIP122 have built in ones.