On May 5th, 1818, Karl Marx, hero of the international proletatiat, was born. His revolution of Socialist theory reverberates throughout the world carries on to this day, in increasing magnitude. Every passing day, he is vindicated. His analysis of Capitalism, development of the theory of Scientific Socialism, and advancements on dialectics to become Dialectical Materialism, have all played a key role in the past century, and have remained ever-more relevant throughout.
He didn't always rock his famous beard, when he was younger he was clean shaven!

Some significant works:
Economic & Philosophic Manuscripts of 1844
The Eighteenth Brumaire of Louis Bonaparte
The Civil War in France
Wage Labor & Capital
Wages, Price, and Profit
Critique of the Gotha Programme
Manifesto of the Communist Party (along with Engels)
The Poverty of Philosophy
And, of course, Capital Vol I-III
Interested in Marxism-Leninism, but don't know where to start? Check out my "Read Theory, Darn it!" introductory reading list!
I think this meme is a little unfair. For the sake of this comment, I am assuming that op is 100% correct about his definitions and I want to stress that I don't claim that "capitalism" is human nature.
Op basically admits in his comments that the general public doesn't have a good understanding of communism or capitalism and consequently how do define them. E.g. He keeps having to explain the difference between capitalism and trade with currency, highlighting the lack of understanding of what capitalism is.
This should make you question what a person means when they say that capitalism is human nature. Do they mean capitalism or their understanding of it? The answer is obvious.
So what do they mean? Given that people don't just walk around saying "capitalism is human nature", it is probably fair to see it as what it attempts to be, a justification. A justification usually follows a critic. And what is that critic? I think it is fair to roughly assume that it is a justification for the usual critic of capitalism. The degradation of human life by encouraging a competitive environment which leads to exploitation and hierarchy. That exploitation is powered by the violence of controlling limited resources.
So the question becomes, could the person saying "capitalism is human nature" mean that humans are competitive hierarchical animals who will use any means to control, oppress and exploit it's environment, including economical violence. If yes, then the age of capitalism is irrelevant and ancient Rome is probably what the person would identify as what they believe to be human nature.
In short, I think the response in the meme doesn't accurately engages with the challenge of the claim and would probably fail to convince anyone and probably makes you seem intellectually dishonest from the perspective of the conversation partner.
I don't believe cowbee is intellectually dishonest, but that they fail to consider the issue from a different perspective, as we all do daily.
The solution to ignorance is education, not humouring the ignorant. People need to have a basic understanding of the world around them if they are to improve it in any manner. Unfortunately, that involves learning some technical terms. Yes, some people will be confused, but realising that you are confused is the first step in learning something new.
Sorry to be like that but ignorance towards what your conversation partner expresses can only be solved by education. And without proper conversations, no education is possible.
One plus one is two, not three or twenty six. If a bunch of people go around thinking that one plus one is three, that has no effect on reality. Such people must be educated as necessary, yes, but we should not avoid speaking the truth out of fear of confusing them.
Completely missing the point are we?
I am saying, if you intend to correct their misunderstanding, you should care for what they understand because then you can probably explain to them how they are wrong. If you don't consider what they understand, you will talk pass each other and leave them as ignorant as they started.
I am not saying, they are right about their definition. I am saying, if you don't approach then where they are, they won't follow you.
Oh no, I understood what you meant. But I feel that OP's approach is correct. They used the words correctly, so that those who already know the meanings can understand what they are saying. Some people did not know what 'capitalism' meant, so they critiqued the meme based on their own understandings. Then OP was able to explain to them the correct meaning.
Returning to my analogy, let us say someone is teaching that 2 + 2 = 4. They can say, 'you already know that 1 + 1 = 2, now multiply both sides by 2'. If a student does not know that 1 + 1 = 2, they can then explain it.
A meme can have only so much text. If they had to derive everything from first principles each time, we would get nowhere.
A memes get shared, consequently removed from context and consequently misunderstood. And removed from context, op isn't around to explain and most people aren't willing to read or write this much.
You are right that a meme has to be somewhat simple. Which is why I believe memes should be seen as a somewhat dangerous medium to communicate politics. The radicalization of the right wing was heavily powered by memes.
As the meme depictes a conversation, it could encourage people to have the conversation like that, and such a conversation wouldn't be productive.
Edit: op btw made it clear to me that they wanted to reach the people "here" with his message and seemingly don't care about possible consequences. Their audience was exclusively intended to be "here", what I would call the in-group and I am considered about the conversation of out-group and in-group.