yekke2: I have heard a number of tirutzim. One is from The Lubavitcher Rebbe TZTZAL notes that the Baal Haggadah refers to them as ARBAAH BONIM (the 4 sons). Even though he is a “rasha” he is still part of “BONIM ATEM L’ASHEM and is still a “ben”.
Another teretz I heard is that the the Torah tells us the question (Shemos Yud Beis passuk Chav Vav) וְהָיָה כִּי יֹאמְרוּ אֲלֵיכֶם בְּנֵיכֶם מָה הָעֲבֹדָה הַזֹּאת לָכֶם and the answer (Shemos Yud Beis passuk Chav Zayin): וַאֲמַרְתֶּם זֶבַח פֶּסַח הוּא לַיהֹוָה. While the Baal Haggadah did not write the second passuk he does write the reaction: “Lachem Vlo Lo”. The Rasha is saying: Lachem? to you? You owe something to Hashem and you are bringing a korban Shelamim which you enjoy eating? If it’s is to Hashem you should bring a Korban Olah which totally goes to Hashem and not a Shelamim?
The Rasha doesn’t want to understand that a davar gashmi (mundane) can be transformed into a davar ruchni (spiritual) and is willing to spread that message. This is why the Baal Haggadah’s reaction is so harsh.
I know it does not totally answer your question. I think only those who are experts in Kiruv Rechokim can really answer your question.