if I just let the whole thing go and act as if the present is all that there is, everyone will be happy.

Forgetting the past is a kind of death. (I'll skip the detailed explanation of that here...) Being asked to just forget is somewhat like being asked to kill yourself. The proper humane thing to do is to remember the past vividly and determine what was done wrong and then right such wrongs; ensure they don't happen again and this is not some personal private journey. We are not solitary animals. We live in groups and nothing much has meaning if done in a vacuum. These wrongs, the understanding of mistakes made must be communicated to the relevant people.

Ultimately the quoted is just typical stupidity. Boring. It is a mindset that can't be reasoned with. A mind that prefers to just not think.

It is Good, so good to think people can be openminded, that they can be reasoned with. But sometimes there's nothing to do but recognize when you're dealing with a monkey. The better a person you are, the harder this is to do. But think of the good people that you could be giving your time to instead. If there are such people...