Even when he says untenable things, this does not reflect his personal view.
Rabbi Gil Student quotes Rabbi David Tzvi Hoffman:
The Karaites famously understand Ex. 35:3 as meaning that we may not have any fire in our homes on Shabbos, not just that we may not kindle fires. Therefore, they extinguish all flames before Shabbos. Ibn Ezra (ad loc.) writes about a debate he had with a Karaite. He argues that the verse only forbids fires on the “day” of Shabbos, and the biblical day begins with the morning. On this last point, Ibn Ezra adduces many proofs. If so, Karaites should permit fires on the evening of Shabbos.
Ibn Ezra could not have meant that he believes that the biblical day begins with the morning. In another work, he writes about this view that: “God should avenge the Sabbath from one who believes this disturbing interpretation. The tongue of one who reads it aloud should cleave to his palate. Also, the arm of the scribe who writes this commentary to Scripture should wither and his right eye weaken” (The Sabbath Epistle, tr. Mordechai S. Goodman, p. 4). Rather, Ibn Ezra must have been arguing about the limits of independent understanding of the Bible. As Ibn Ezra wrote (Ex. 35:3): “I only mentioned this because an understanding person can interpret Scripture in many ways. Therefore, regarding all commandments, we need a tradition and Oral Torah.”