I'm referring to cancelling classes. We do it for MLK day, but not Columbus or Veterans' day.
The policy should be consistent on national holidays.
Firstly, why do you not advocate attending classes on MLK Day: that too would re-establish consistency.
I am not making fun of your desire to skip, rather to attend classes. What you may or may not know is that universities are notorious for NOT granting days off. Most proudly declare that they were closed only for a couple unscheduled days in a couple of centuries. So granting release here is more serious than at a commercial firm, for instance.
Further, a comparison of holidays is very difficult: each of us has a different attachment and weight given to different holidays, don't we? In the case of MLK day, it was argued that, at least during the transition from the pretty bad past, where Black people needed to see that America celebrates them as well. MLK Day has gain prominence of other holidays largely for that reason.
Now, if you advance a course of action, you should offer arguments (besides consistency: you do get a Thanksgiving break and don't complain about that) that address these points and show how they can be addressed better.
P.S. Say hi to the Locust Walk for me.