There is a concept of a single issue political party.
There are also many people who are "single mitzva" Jews. For them, if you keep this mitzva, you are a good Jew. If you don't, regardless of how many mitzvos you keep, one is a severely flawed Jew.
This is an egregious error. There are 613 mitzvos from the Torah and thousands dirabanan. Judaism cannot be constricted to one lone mitzva - important as it may be.
וד"ל.
