Pesachim 73 - A destroyer on Shabbat

If people cannot eat the Passover offering's meat, and one slaughters the sheep for them, his act makes the sacrifice invalid. We had this rule earlier. If he, moreover, does this on Shabbat, he is liable for a sin-offering. However, what did he do? There is a view that one who acts destructively on Shabbat does not violate Shabbat. Only constructive acts count. If so, why is he bringing a sin-offering?

Rav Huna bar Chinana asked his son to ask Rav Zerika this question when he sees him. The answer was: here is what he accomplished, true, the sacrifice is invalid, but at least, if they mistakenly put its parts on the Altar,  the parts can stay there.

The next question: if he slaughtered a sin-offering on Shabbat, outside the Temple, and as an idolatrous offering, he did many wrong things. But why is it counted in particular as a Shabbat violation? What positive effect did he accomplish? - At least, those who will be eating it are not eating a piece cut from a live animal - which is prohibited alike for Jews and non-Jews.

Art: Shabbat by Mark Chagall