I have been reading his works and it is absolutely incredible how little has changed in Protected content . There's a good reason this is not taught in American schools. He also refused to pay his taxes to avoid supporting the Mexican War and was imprisoned. Excerpts below taken mainly from Walden and Civil Disobedience.
On being a US Citizen:
"How does it become a man to behave toward this American government to-day? I answer, that he cannot without disgrace be associated with it. "
On Government, Army, and War:
"The standing army is only an arm of the standing government. The government itself, which is only the mode which the people have chosen to execute their will, is equally liable to be abused and perverted before the people can act through it. Witness the present Mexican war, the work of comparatively a few individuals using the standing government as their tool; for, in the outset, the people would not have consented to this measure."
On the US Government:
"This American government — what is it but a tradition, though a recent one, endeavoring to transmit itself unimpaired to posterity, but each instant losing some of its integrity? It has not the vitality and force of a single living man; for a single man can bend it to his will. It is a sort of wooden gun to the people themselves."
On Pacifist Non-Resistance:
"Let not our Peace be proclaimed by the rust on our swords, or our inability to draw them from their scabbards; but let her at least have so much work on her hands as to keep those swords bright and sharp."
"Most of the luxuries and many of the so-called comforts of life are not only not indispensable, but positive hindrances to the elevation of mankind."
"I cannot believe that our factory system is the best mode by which men may get clothing. The condition of the operatives is becoming every day more like that of the English; and it cannot be wondered at, since, as far as I have heard or observed, the principal object is, not that mankind may be well and honestly clad, but, unquestionably, that corporations may be enriched."
On being taxed, but only having freedom of speech/right to peaceful assembly:
"How can a man be satisfied to entertain an opinion merely, and enjoy it? Is there any enjoyment in it, if his opinion is that he is aggrieved? If you are cheated out of a single dollar by your neighbor, you do not rest satisfied with knowing that you are cheated, or with saying that you are cheated, or even with petitioning him to pay you your due; but you take effectual steps at once to obtain the full amount, and see that you are never cheated again. Action from principle — the perception and the performance of right — changes things and relations; it is essentially revolutionary, and does not consist wholly with anything which was. It not only divides states and churches, it divides families; ay, it divides the individual, separating the diabolical in him from the divine."
These are only small excerpts but there is so much more.