Was horrible?

Are you forgetting about modern western imperialist adventures such as Iraq and Afghanistan, entering their 16th year? Where millions of civilians were and are still being killed, injured, displaced, tortured and all around stomped on in terms of human rights, led by some of the most powerful western nations in the world. These wars were cheered on by a good chunk of US and UK citizenry for years before they conveniently faded into the background.

http://www.psr.org/assets/pdfs/body-count.pdf

That's even ignoring the direct relations of these invasions to the more recent conflicts in Libya, Syria, and ISIS, the boogeymen armed and created by the same people who started these wars not long ago.

Western imperialism is alive and well.

Pretty sure Afghanistan attacked the U.S. first.

And that western nations are supporting freedom fighters in Syria.

I guess it's because of the timescales.

I am assuming the people who celebrate the wars of kings in their lands are more than 500 years old while Western colonialism sort of stopped just 50-100 years back.

So the Western atrocities are still fresh in the mind while people forget the 1000 year old atrocities.

For example, the crimes of the British during the Mau Mau rebellion are within living memory. And, importantly, the current British government is a successor to the one that oversaw those crimes.

And conversely several African states have governments that either took part in the fight against colonialism personally, or are from families where family members fought the colonial powers.

E.g. when looking at Robert Mugabe's hostility towards Britain in particular (without wanting to justify his authoritarianism and violence) it is worth considering that he fought for independence, and though Britain as responsible for allowing Rhodesia to happen.

I guess this does make sense. I wish people stop glorifying violence distance past, recent past or present.

What Western conquests were seen as evil out of interest? You mean colonisation? Or other wars?

To take a particularly bad one that relatively frequently comes up, consider the Congo Free State [1], which is considered bad enough by some still that a statue showing king Leopold II being celebrated by the Congolese was vandalised by someone chopping off the hand of one of the African characters to symbolise the history of chopping off the hands of those who refused to work the rubber plantations.

But the list is massive.

[1] https://en.wikipedia.org/wiki/Congo_Free_State

Colonizations, almost all of my friends from international communities had their countries colonized by Western powers. A lot of them still blame colonization for current problems in their countries.