[2019] how do you proceed when you meet pre-made toxic teammates tkers ?

Instead of griefing back at griefers, you should be utilizing the report a player function[support.ubi.com] in-game. Alternatively, you can report any screenshots or videos you have directly through a support ticket[support.ubi.com] via a Conduct Report.
Each report is reviewed on a case by case basis, and we are unable to discuss the outcome of an investigation with anyone except the reported player.
I'm sorry to hear about your negative experience with Siege and assure you the R6 team is continuing to monitor toxicity in the community.