<span>I think he probably meant that the Constitution is not to be set in stone and should change to fit the times, which is my the Founding Fathers put in the Amendment process.
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"A constitutional door is left open" refers to the question of whether an action is constitutional or unconstitutional. There is gray area that needs to be discussed.
Martin Luther King Jr. was a believer of peaceful protest. Every single one of his protestant gatherings were meant to be peaceful. a quote from from one of his speeches shows this:
I have decided to stick with love. Hate is too great a burden to bear.
The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy.
In the end, we will remember not the words of our enemies, but the silence of our friends.
unquote.
This excerpt proves that he was a peaceful protestor.
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