Let's bracket the "was the USSR in the right?" question, and let's ask the "how brutal was the Soviet clampdown on these two uprisings?"

• 1956 Hungary: 2000-3000 killed by the USSR
• 1968 Prague: 137 killed by the USSR

How does this compare to clampdowns by NATO countries (excluding the US)?

• Indonesian National Revolution against the Dutch: 100 000 Indonesians killed by the Dutch

• Algerian War of Independence: 250 000 killed by the French (French estimate) - 1.5 Million (Algerian estimate)

• French War against Vietnamese Independence: 200 000 dead

• Portuguese Colonial Wars: 70,000–110,000 civilians killed by Portugal

• Mau Mau Uprising against the UK: "Officially the number of Mau Mau and other rebels killed was 11,000, including 1,090 convicts hanged by the British administration. The Kenya Human Rights Commission has said 90,000 Kenyans were executed, tortured or maimed during the crackdown, and 160,000 were detained in appalling conditions. "

This is a non-exhaustive list with estimates. The actual brutality is not conveyed. The war crimes are often comparable to the Waffen SS.
You get the idea: the colonial powers were incomparably worse.