I've found a quote for repressive anti-racists:
"The political core of any movement for freedom in the society has to have the political imperative to protect free speech." —bell hooks
For repressive Democrats, here's one from Clinton's Secretary of Health and Human Services:
"You can't have a university without having free speech, even though at times it makes us terribly uncomfortable. If students are not going to hear controversial ideas on college campuses, they're not going to hear them in America. I believe it's part of their education." —Donna Shalala
For repressive socialists, an anarchist poet:
"Freedom of speech is always under attack by Fascist mentality, which exists in all parts of the world, unfortunately. —Lawrence Ferlinghetti
Refraining from silencing the people you see as enemies falls under a truth shared by all major religions and many great thinkers: love your enemy. A few quotes:
“It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. The other is mere business.” ― Mahatma Gandhi
"Hatreds never cease through hatred in this world; through love alone they cease. This is an eternal law." —Buddha
"He whose heart is in the smallest degree set upon Goodness will dislike no one." —Confucius
"I treat those who are good with goodness, And I also treat those who are not good with goodness. Thus goodness is attained." —Lao Tzu
"The good deed and the evil deed are not alike. Repel the evil deed with one which is better, then lo!, he between whom and you there was enmity shall become as though he were a bosom friend. But none is granted it save those who are steadfast, and none is granted it save a person of great good fortune." —Qur'an 41.34-35
“Now there is a final reason I think that Jesus says, "Love your enemies." It is this: that love has within it a redemptive power. And there is a power there that eventually transforms individuals. Just keep being friendly to that person. Just keep loving them, and they can’t stand it too long. Oh, they react in many ways in the beginning. They react with guilt feelings, and sometimes they’ll hate you a little more at that transition period, but just keep loving them. And by the power of your love they will break down under the load. That’s love, you see. It is redemptive, and this is why Jesus says love. There’s something about love that builds up and is creative. There is something about hate that tears down and is destructive. So love your enemies. (from "Loving Your Enemies")” ― Martin Luther King Jr., A Knock at Midnight: Inspiration from the Great Sermons of Reverend Martin Luther King, Jr.
My favorite gospel is Luke's, so here's his version of Jesus's advice, Luke 6:27-36:
27“But I say to you who hear, love your enemies, do good to those who hate you, 28bless those who curse you, pray for those who mistreat you. 29“Whoever hits you on the cheek, offer him the other also; and whoever takes away your coat, do not withhold your shirt from him either. 30“Give to everyone who asks of you, and whoever takes away what is yours, do not demand it back. 31“Treat others the same way you want them to treat you. 32“If you love those who love you, what credit is that to you? For even sinners love those who love them. 33“If you do good to those who do good to you, what credit is that to you? For even sinners do the same. 34“If you lend to those from whom you expect to receive, what credit is that to you? Even sinners lend to sinners in order to receive back the sameamount. 35“But love your enemies, and do good, and lend, expecting nothing in return; and your reward will be great, and you will be sons of the Most High; for He Himself is kind to ungrateful and evil men. 36“Be merciful, just as your Father is merciful.