MLK did not give up his right to speak and act freely, he exercised it. There was a huge cost, yes. His position is also unique to him and his circumstances, and his sacrifice accomplished a goal unique to his time. But its also different from voluntarily giving up some rights on a daily basis and being sent to war with no ability to question it to enable people like MLK to actually do what he/they did. Without those who went before him, in The Great War and WW2, and those who actively volunteered during Korea, Vietnam, and the Gulf Wars -- not to mention UN peacekeeping -- he would not have had the opportunity to do what he did.

You can quit your IT job on a dime, tell your boss where he can go, and engage in the political speech of your choice, without losing your freedom. You go into your job knowing what it will entail, and can walk out at any time. You will not be asked to take a bullet, or scrub a squeaky clean floor for several days with a toothbrush without the ability to say "no" or land in the brig.

Here, willingly stand between me and an armed terrorist for your paycheck on Friday. Go ahead.