How do assumptions relate to the process of critical thinking?

Question

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PLEASE HELP ME EVALUATE THIS ARGUMENT
Recently, people have been arguing that marijuana should be legalized because it is really no different than alcohol. as convincing as this argument seems, it is too flawed to be taken seriously. Thoughthere are similarities between the two substances, apart from its medicinal use, marijuana is consumed by individuals for only one reason in this country: intoxication. On the other hand, alcohol is used for a variety of purposes that have nothing to do with getting intoxicated. Alcohol is used in celebrations such as marriages and anniversaries, in religious rituals, and as a gourmet element.