Unfortunately, it is their right to do so. I completely disagree with what they are doing, but grateful we live in a country where we can express ourselves without fear of going to jail.
As the old saying goes, 'I may not agree with what you are saying, but I will defend to the death your right to say it.'
With that being said, to all those that want to live here but desecrate our flag (which ultimately desicrates our beleifs on which this country was founded), fuk 'em.