There can be a lot of crossover between memes that are about "politics" and those about social justice. So, there are several headings I have in each section that I just about as easily could have included in the other section. The heading "politics/parties" obviously belongs in the political memes section, though perhaps somewhat ironically, I decided the heading "political correctness" was a better fit in the social justice section. Other headings in the SJ section that can be political in nature include "abortion", "activism", "classism", and... well, to some extent, all the headings. Some that I put in the political section that can involve social justice include "immigration", "police", and again, all the headings.
See also memes I made, which includes its own heading for political memes that I don't find serious enough (or general enough) for this page.

memes that might need some (pop cultural) context:

"Assimilation": I made this to demonstrate the problems of "assimilation" versus multiculturalism (and to reference the fact that "colorblindness" is problematic). I had to search for a picture of the Borg (a group first introduced in Star Trek: The Next Generation), though I think the pic I ended up using might actually be of cosplayers. If so, I'm sorry about that, but it was the best Borg pic I could find.

"Gru's plan": This is one I made using a popular meme format with the character Gru from the movie Despicable Me.

"The Sound of Music": The title is self-explanatory, I'd say. (I didn't make it.)

"Liberal prof vs. alt-right": This uses a screenshot from one of the "Indiana Jones" movies; I think it must be "Raiders of the Lost Ark." (I didn't make it.)

"Wolfenstein": This is based on a series of video games, which I haven't played. (I didn't make it.)

"Confirmation bias": This one I made using a popular meme format with the character Philip J. Fry from Futurama.

"Blue wave": This is one I made using a screenshot of a 1980s Coke commercial featuring the character Max Headroom.

"You go too fast": This is one I made using a bunch of screenshots from Good Omens, featuring a demon named Crowley and an angel named Aziraphale. The final two frames are from a scene where Crowley offers Aziraphale a ride, and the latter declines, saying, "You go too fast for me, Crowley." It just seemed like something that could make a good metaphor for how fucking slow conservatives are to accept social change.

"Cats: Butthole Cut": This is an idea I had based on people wanting to see a rumored "butthole cut" of the 2019 movie "Cats," but I didn't make the meme myself. I mentioned the idea to my friend Holli, and she made it.

"Reasons Trump is a bad president": This is a screenshot from The Late Show with Stephen Colbert. (I didn't make it.)

"Remember the 80s?": This is one I made using a screenshot from Family Guy, which was parodying old Pepperidge Farm cookie commercials

"The Smirker": This is one I made by editing Trump's face into a panel from the comic book Transmetropolitan.

"Tastyfish/poisonfish" and "Terms without a tyrant" are both screenshots from The Simpsons that I altered.

"Trump Supporters": This is one I made with screenshots from an episode of Futurama, in which the character Bender was lying to the Planet Express Ship, but (she) believed him.