What is it about the wicked son's question that marks it as the question of the wicked son? The standard haggadah text makes the question מָה הָעֲבֹדָה הַזֹּאת לָכֶם all about that last modifier, lachem velo lo. Though when contrasted with the wise son's question, it is momentarily problematic, in that he also asks מה העדות והחוקים והמשפטים אשר צווה ה' אלקינו אתכם, but this can be summarily dismissed when we note the likelihood that they were working off a different girsa of the pasuk, which had otanu rather than etchem. (See Yerushalmi Pesachim 70b. There have been many unnecessary and incorrect divrei Torah based on this, but they may be useful to derive and convey an important message, even if this was not the message which was originally intended to be conveyed.) There are other differences, of course, one important one being that the question הָעֲבֹדָה rather than העדות והחוקים והמשפטים implies that it is bothersome, which Yerushalmi stresses as מה הטורח הזה שאתם מטריחין עלינו בכל שנה ושנה. It is possible, and indeed the case, that the Torah's response to a particular son is not necessarily offered to that son. Thus, the response is baavur zeh, which occurs elsewhere. The pesukim which put up the "wicked son's" response are in Shemot 12:
But what about the response -- that since he takes himself out of the community, you tell him that if he were not there, he would not have been redeemed? This certainly can be just a derasha on lachem followed by the response culled from elsewhere, that one can respond baavur zeh asa Hashem li, which is a normal response, but with certain words stressed to form a meaningful retort. But despite the fact that it is not the response in the haggada, perhaps the local response to this question in Shemot 12 can shed light on the type of response offered. After all, the answer is that the purpose of the sacrifice, the zevach Pesach in Mitzrayim, is to identify oneself as an Israelite. And in makkat bechorot, Hashem skipped over all the Israelite houses which in which people chose to participate in this and declare that they were Israelites. But any house not so marked would presumably have been smitten together with the houses of the Egyptians. And this, says the pesukim, is the purpose and function of the zevach Pesach. From the response, we can then extrapolate the nature of the question.
And indeed, not because of merit or lack thereof would he not have been saved had he been present. Rather, if he had been there and not joined the community in this, and identified as part of the community, he would not have been saved, for there would not have been the blood of the Paschal offering on the mashkof and the two mezuzot.
There might be some homiletic message we can derive from this, if we wished to, about the importance of participating in some ritual just to participate as part of the community.