"You are such a capitalist." Depending on emphasis, the phrase can mean:
You are a pig who doesn't care about human beings and only cares about the bottom-dollar and making a profit.
I'm pleasently surprised you recognize the fact that, in many cases, capitalism increases efficiency and lowers costs and matches needs/wants to payment. Capitalism insures that businesses stay in business long enough to make many lives better off, as opposed to what would happen if they started giving hand-outs to a select few.
Here's the thing. When used in every-day conversation with friends or loved-ones, "Capitalism" almost ALWAYS means the former - ie, it has a very negative connotation. Why? Because economists have not explained benefits well enough? Or maybe because the negatives of capitalism are more visible?
BUT, economists and people with an econ background may often mean the latter more positive meaning of capitalism.
SO, now imagine you get a gathering of three veterinarian friends (one who may be your significant other) and one economist -- and the vets explain why it annoys them to no end how many clients expect free pet services and actually get upset when the vets don't cut huge deals for them and their sick pet. They exclaim that they charge whatever is necessary to make the pets better off. Now imagine, that the economist responds (because he/she has to relate the situation to what they know), "You are such a capitalist."
... FYI, if you are in a gathering of non-economists, don't use the word "capitalism." No matter your inflection, no matter your tone --- sparks will fly.