How do those who consider alcohol impure respond to the Companions spilling it in the streets after it was forbidden, despite the fact that discarding impurities in the streets is prohibited, and given that the noble verse mentioned Maysir (gambling) and Ansab (altars), neither of which are inherently impure substances?

The majority of scholars hold that Khamr (wine/intoxicants) is ritually impure (najis al-ayn). Their evidence is the consensus of the predecessors (Salaf) and successors (Khalaf) regarding its impurity, the prohibition of its sale, and based on the verse: "O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone altars [to other than Allah], and divining arrows are but defilement from the work of Satan, so avoid it that you may be successful" (Quran 5:90). The fact that some of the other mentioned items are not considered physically impure does not negate the verse's indication of the impurity of Khamr. The Companions' pouring of Khamr in the streets does not indicate its purity; rather, it was due to the necessity of not having other places to pour it, combined with its small quantity, and to publicize its prohibition and destruction.