E2E encryption doesn't need an argument for it, it has specific, valuable and demonstrated uses, and I reject the premise of the question that the technical and business use cases for it need an accompanying rhetorical justification.
The people asking for the arguments are not people who can be persuaded by argument, they are looking for ways to drive another agenda. It's disingenuous and not a matter of reason.
To respond to the question itself, let's start with what we actually do. We make the stuff people actually want, and thanks to abuses by authorities around the world, today they want privacy and trustworthy tools. We build things that facilitate growth and massive improvements in quality of life for literally billions of people around the world. That growth comes from building the things they both want and trust, and use each day to improve the quality of their own lives and of their families. I would encourage governments to get better at offering the same things.
The extreme cases cited in the OP are abused by people with agendas to use them as levers to assert their narrow interests, and not because they want to solve those particular problems. Parading victims of abuse and violence to bolster a narrow surveillance agenda is the rhetorical equivalent of using human shields. Hardly anyone is actually stupid, and everyone sees it. Further, why would you ask technologists to presume good, altruistic and aligned intentions in governments who want to conduct surveillance, yet not among ourselves and our users of encryption services? We can't make that altruism generalization about our own governments, let alone ones in other markets. I would reject this particular premise in being asked to make an argument "for," as well.
The question, "I need you to justify your view to me, and with it, these objectively terrible things" is disingenuous.
The short answer is technologists do not have the solutions to niche social and political problems any more so than anyone else. Terrorism, abuse, and porn exist independently of tech. The "arguments," against E2E encryption are made by people who don't have responsibility for the outcomes of their efforts, and are using these threats to deflect that and make others responsible for them.
If we all gave up E2E encryption, the value people entrust to networks would be reduced to where it would derail and destroy the economic growth trajectory which that trust facilitates to improve peoples lives. The solution is not for tech to do less of what people demonstrably want and willingly pay for, it's for governments to be smarter about their own roles and responsibilities.
If you want to solve the problems of abuse and terrorism directly, there are a ton of solutions that don't involve destroying the trust people have in each other that has improved our collective quality of life immeasurably in the last 30 years.