(1) I'll clarify myself: When I write about imperial politics, I mean the western oligarchy, not the people in the west. Yes, the people in the west have been made complicit in the crime of the oligarchy, but they are also (in a sense) a victim. For example: The oligarchy in England was not able to conquer India alone. Nor would they have risked their lives in the process. For that they have used the people. First they gave more money and power (military grades) to soldiers who would go to another side of the world and risk their lives to fight some foreigners who didn't pose any threat to their families or their country. After these soldiers have done their part, using the same scheme ("more money and power"), administrative officers were sent to administer the looted and to secure the power position of the oligarchy. Again, both groups (soldiers and administrators) were victims as well, risking their lives for a tiny bit of money and power compared to the profits and power gain of the oligarchy. And that pattern continues to be used today. Look for example at the testimonies of US soldiers who were in Iraq (on YouTube [1] [2] [3]). These guys are now physically and psychically sick from the war they were sent to wage for the US oligarchy and the system has no purpose for them (prior to them entering the service and now), but they are still humans with compassion.
(2) The argument about science and technology is a complex one. Yes, there were Romans but we don't know sources for their scientific and technological advancements. We do know that, after the Romans, the west fell behind burning books and "heretics", and that the Islamic world was leading in science and technology during that time. We also know that when the west (the western oligarchy) came back with trade, it was followed by the imperial politics. And that continues to exist today as well. Look at the USA: It has made a system where it offers free information on US universities in their embassies. Then the young bright people, many from countries the US oligarchy has destroyed economically, so see no future in them and they come and study in the US. Later, in universities, research facilities and companies (as employees and [co]founders) they become (known) sources for scientific and technological advancements in the US. By doing that, he US is robbing already robbed countries: (a) of their future elite that would build a home country again; (b) their home countries have paid for their pre-tertiary education. And other western countries (oligarchies) do the same.
(3) Considering what I wrote under (1), it were not all "Westerners" but the western oligarchy who was the driver of the slave trade. Also, even thou there was (and still is) slave trade in Africa, the sheer scale, brutality and profit extraction out of slaves by the western oligarchy is not comparable with "intrarace" slave trade.
(4) Yes, white guilt is wrong. You are right that it is a tool of warfare, a warfare between poor people in the west and poor people in other countries, staged by the western oligarchy. No rich people fight in a war, not in the past, not now. And you are right that it is "a psychological/social weapon and an excuse to persecute individuals for things they did not do themselves". There is only the guilt of the oligarchy. If (and only if) the people in the western world say no to being peons in this game their oligarchy plays with their and the lives of other people, then they would do more for the peace in the world than all UN programs for the "third world".
[1] https://youtu.be/gdn3bIfP7fk
[2] https://youtu.be/VwwMF6biCJU
[3] https://youtu.be/SOqPBC3ZMn8