CW as the subject matter might be heavy for some.
To begin with I'll clarify that I have been the recipient of a lot of vulnerable people confiding in me in my life. I know what it is like to have people suddenly dump very serious and upsetting problems on me, unsolicited. I also suffer from a lot of trauma myself, and so being trauma dumped on can be triggering of my own trauma. So yes, I can understand why trauma dumping is frowned upon and considered toxic.
However, perhaps in the age old tradition of terms being taken by the general public and misinterpreted into something almost the opposite of it's meaning, I see the term now constantly thrown in a harmful way around by the general pubic. The term "Trauma dumping" is now used to shame those with trauma who are reaching out for help at their lowest. It's used in any situation where someone opens up about their traumas.
There is something very messed up about a society that pretends that "You shouldn't keep everything to yourself, it's okay to ask for help." That in turn punishes and shames people who finally do ask for help as "Eww, stop trauma dumping. Your problems are a burden on me actually, so shut up and suffer in silence or pay someone to fix you! You're selfishly dragging down us healthy normal people!". I think this will lead to a lot of people in society being taught to hide their problems out of fear and shame. It feels wrong.
Anyway, I can understand if this is a hot take and maybe I am projecting. I can understand both sides, but ultimately it leaves a sad pit in my stomach thinking that vulnerable people are made to think no one cares about them.
The demonising of empathy is scary. Real "Don't show pity for the homeless, they're just taking advantage of your kindness." hours.
Your observation is recognized. Probably caused by a structural lack of social support leading to volcano-like situations.
One can only hope that enough empathy is found in the recipient of a trauma dump. If you are and having trouble, feel free to slow your peer down a bit and take a break if needed. If you feel overwhelmed, do not hesitate to tell them you would love to be there for them even more and need a little time to process yourself.*
If you have a lot of trauma stacked up and feel like you may explode, time to choose a part of it to share with someone -- not all at the same time if you can. Even though your own emotions are incredibly difficult to bare, make the effort to also consider how the person you want to talk to is feeling and can bare.
All in all a very difficult thing. Fortunately there are still so many people who are willing and able to support each other.
Oh, remember: Psychologists often go to therapy every now and then or structurally if required to be able to keep helping clients with all kinds of emotional stories.