I posted this last year, I think this is worth repeating.
The Beis Halevi explains the רשע's question as follows. He says that the רשע is asking why do we need to do the mitzvos nowadays. Who wants to bring an animal sacrifice in 2005? The רשע understands why the Jews in Egypt brought it, but we have grown up, who needs all these anachronistic miztvos? The answer given is "בעבור זה עשה ה לי בצאתי ממצרים". The Beis Halevi asks this is strange answer? I would have expected something like, because hashem took us out of Egypt we do these mitzvos. He explains this as follows. We see from many sources that the Torah preceded the creation of the world. We think in terms of cause and effect. Because we left Egypt we have Pesach and all the mitzvos. However, this is incorrect. The mitzvos existed before the world was created. The events unfolded the way they did because they had to, so that the mitzvos in the torah would make sense. Based on this we understand the answer, "בעבור זה" because of this, the Torah, עשה ה לי, Hashem made the events of יציאת מצרים happen. This answers the רשע, that the mitzvos preceded the events and are not anachronistic at all. The Mitzvos are not based on the events, rather the events are based on the mitzvos, and therefore the mitzvos are timeless.