Depends on what you mean by "colonialism."

Bartolomé de Las Casas condemned Columbus's cruelty and rapacity toward the Taino during Columbus's own lifetime. Didn't stop him from supporting conversion and African slavery (though he repented of the latter later in life.)

There was, from de Las Casas all the way down into the twentieth century, a strand of colonial thought that asserted that colonialism was justified if it made natives' lives better - that manifested in the civilizing mission/ethical policy/white man's burden, etc.

European rejection of colonialism as altogether morally bad (AFAIK) seems to be a 19th-century project. The French were less than clear about Haiti, but after the French Revolution there was a growing condemnation of colonialism and imperialism as immoral primarily emanating from the Left - socialists, anarchists, liberals, democrats, and republicans often framed their criticism of monarchy and aristocracy to include a condemnation of colonialism, though many of them thought that bringing colonies into the world system was either desirable or (in the case if Marx) lemantably unavoidable.