I know a whole lot of conservatives that make great parrots too. Both sides have plenty of true believers that parrot what their favorite source of information is and really don't have any free thoughts outside of that.
I won't disagree with that. I mentioned above I have probably done it myself. IMO, when you are exposed to a new issue, you go from "I don't know anything" to "I agree with that line of thought" to "here are the reasons why this is correct". When people are in that middle ground, it is easy to fall into parrot mode. Some people are better at expressing things in their own words than others. Later you learn more about the issue and about your own reasoning. Some people never get out of that level of thought, some people pass through it very quickly.
And some people parrot someone else's words simply because it captures the meaning well enough and there is no time to go into detail. If meme had the full description of an issue, no one would read it.
....so FOUR LEGS GOOD, TWO LEGS BAD!!