Great article yesterday in the WSJ about this and to sum it up progressives want to ruin any holiday that celebrates AMERICA:

"For all the talk about the “real” Columbus, protesters are unlikely to take up the invitation for further study and debate. For the defining fact of the modern progressive is that he is a pest, and what he wants here is simply to ruin any public celebration an ordinary American might enjoy, whether it be Italian-Americans celebrating Columbus or NFL fans sitting down to watch a game" (writes William McGurn).