Yes, in fact, there has been an entire movement called "anti-colonialism".

The Spaniard Bartolomé de Las Casas wrote in 1552 his "Brevísima relación de la destrucción de las Indias occidentales" (Report about the destruction of the West Indies) and he had heavy critics such as Michel de Montaigne.

Since the 16th century, the "Leyenda Negra" (Black Legend) began to circulate as new conception of history which included a strong criticism of the Spanish colonial policy. However it wasn't uphelt in a humanitarian but rather a political spirit in order to discredit Spain, so it includes many exagerations and biased opinions, although the basic criticism of the Inquisiotion and the general barbarism in the New World had surely a certain legitimacy.

The portugese Jesuit António Vieira criticised the colonial nuisances in Brazil of the 17th century and fought against slavery.

In 1788, the parisienne Société des Amis des Noirs was founded. Their main goal was the abolishment of slavery.

Guillaume Thomas François Raynal, one of the most prominent writers of the period of enlightenment, wrote his famous book "Histoire des deux Indes" ("History of the East and West Indies" - referring to America and India) which caused enormous termoil for him, leading to his flight.

A criticism of colonialism in general was rare in the 19th century. Criticism often adressed certain excrescences of colonialism, especially slavery. The Frenchman Victor Schoelcher advocated against slavery in the USA before the time of 1848.

In Germany (the German Confederation to be more precise), you have people like Alexander von Humboldt who travelled around the Americas and formulated his observations about Cuba in a very critical book which was partially censored in Europe. Heinrich Barth travelled around Africa and witnessed the brutal hunts for slaves. He criticised the British Empire but stayed unheard since the German interest in colonies only began later with Bismarck and Wilhelm II.

The author Eduard Douwes Dekker criticised the Dutch policy in the Dutch East Indies, the modern Indonesia.

Other notable people are Lord Curzon, August Bebel and of course Rosa Luxemburg who saw colonialism as a general phenomenon of Imerialism. Karl Kautsky had similar views about the origin of colonialism.

In 1931, there was the Paris Colonial Exposition which found a large public resonance, but also led to a counter-exposition by intellectuals and artists called the "Ligue de Défense de la Race Nègre", led by Tiemoko Garan Kouyaté and the PCF.

In 1934, the former colonial official George Orwell published his book "Burmese Days. He had to publish it in New York because severl British publishers refused to do so.

In 1935, intellectuals criticised the Italian invasion of Ethiopia in their "Manifeste pour le respect de la Loi internationale" (Manifest for the respect of international law).

After WW2, many former colonies gained their independencies and we are experiencing a general change in foreign policy.

On September 2nd, after the successful August Revolution, Ho Chi Minh proclaimed the Democratic Republic of Vietnam. The french attempt to reestablish their colonial regime caused the Indochina War which resulted in a defeat for the French in 1954 with the Battle of Dien Bien Phu. This defeat had a signaling effect for other anticolonial movements.

India gained independence in 1947; in the same year, the rebellion in Madagaskar against the French colonialists commenced.

In 1952, Great Britain crushed the Mau Mau Uprising in Kenia, but the international scandal about the internment camps led to the final independence.

During the Algerian War, the Réseau Jeanson supported the FLN. In 1960, French intellectuals refused their military service and formulated it in the Manifesto of the 121.

In 1961, the Portugese Colonial War resulted in the independence of the Portugese colonies in Africa. The Carnation Revolution 1974 led to the overthrow of the old Estado Novo regime and the new left-wing gouvernement also gave the overseas provinces their independencies which brought the portugese colunial history of 500 years to an end.