Final answer:
Karl Marx compared religion to an opiate for the masses, seeing it as a tool that justifies and upholds social and economic inequalities.
Step-by-step explanation:
Karl Marx compared religion to an opiate for the masses. He saw religion as an ideology that justifies inequalities and as a source of false happiness which helps people cope with economic difficulties in capitalist societies. According to Marx, religion also supports the political and economic inequality of the working class by prompting them to focus on an afterlife of comfort instead of challenging their current socioeconomic conditions.