It sounds like there is a law in MA that limits the recovery for uninsured drivers even when they are not at fault.
Not to my knowledge, but Massachusetts is somewhat unusual in that the minimum insurance law also has a minimum bodily injury limit by uninsured motorists on HIS policy. It's the same as the "bodily injury to others" limit at 20,000/40,000. But it doesn't mean that the coverages are additive. If the other person has insurance (even if only at the 20/40 minimum), you don't get to collect from your mimimum required uninsured motorist coverage. Though that brings up a good point, he should consult his own policy to see if he has additional coverage for an UNDERINSURED at fault driver.