I am not anti-cop, but I am anti-thin blue line and definitely the blue line on the American Flag is as disgusting to me as someone burning the flag. I feel you are putting your cause in front of the United States. Both are covered by the 1st amendment and I will protect that, but I don't like it.
My issue with the Thin Blue Line is it is simply cops protecting other cops when they do dumb stuff. Just this year, too man good cops died because some idiot in another state killed someone by accident and retribution came to innocent cops thousands of miles away.
In every profession, there are good and bad. Weed out the bad, not protect them.