This is a massive over-reaction. The policies his government has put forth over the last four years have shown he is anything but racist. What he did was racist and stupid, but he owned up to it and apologized - certainly more than you can say about other world leaders. I am getting sick of this persecution of people for past mistakes to score political points, but it is the new norm, and will only become even more normalized as we live in a new age where political candidates (or any public figure for that matter) have their entire past on social media to be scrutinized.
The problem here lies in hypocrisy. This is an example of why the virtue-signaling, holier than thou posturing of liberal politicians like Trudeau today is so frustrating and dangerous, and only leads to further polarization and the election of populist figures. For all of the terrible things that done Donald Trump has done, at least he is unabashedly a piece of shit, and doesn't pretend to be perfect.
In summation, this incident shouldn't taint your entire perception of Trudeau, and certainly does not make him a racist. Is he a stupid and unqualified moron, yeah, of course, but he's not a racist.
Another thing to consider is that Canada is a parliamentary democracy - the real issue will be reconciling voting for Liberal candidates who are brown, while these photographs of their leader lie in the background. At the end of the day, I don't know if it is quite as damaging as it would be for a Presidential candidate who is directly voted for.