I know you listed your English as on the "level 2", but don't worry, you seem to be doing nicely otherwise, judging by the same page - so don't be taken aback. I just wanted to know if you were aware of what you wrote, and think it's an interesting case.
 I would write that sentence simply as "Theoretically I am an altruist, but only by word, not by my actions.".
 PS. You can reply to me on this same page, as I have it on my watchlist.