Is there any affordance given for the possibility that some of this military technology will actually be used for good?
I think that technology that can be used to protect people, especially civilians, should be developed. I know that I personally draw the line at weapoms platforms and weapon systems. You may develop and build them with the best intentions in mind ("we're at peace and this system is only a necessary deterrent"), but recent history tells me that once these systems are built and sold, they will be used by someone, somewhere to shoot at other people. Even the oh so pacifist Germany sells a lot of weapons and I think every type of weapon system sold to another country by Germany since the second world war has seen some action.
I think a lot of people in tech work on really questionable projects that create huge social ills, then talk about "Well, at least we don't build weapons!" -- ignoring that when measuring human suffering, their unrestrained manipulation and exploitation causes much more than weapons of war do, in practice.
So when unqualified, I tend to hear your argument as simply trying to hide the messiness of what you do, rather than than it's inherently more ethical than building weapons would be.
tl;dr: I don't believe the military is less ethical, I think they're just more honest about what they do.
I am not sure of this discussion of social media is framed correctly. At its core, all this social tech tries to satisfy the very basic human need for communication in novel ways. There is nothing bad about trying to achieve that. But somewhere along the way something unintended and bad happened. We need to find out what it is and how to fix it as a society. The underlying tech and concepts will never go away again. It can be used for good. We realized too late that we failed to use it properly.
It's a standard human fallacy, which I've made numerous times: we look at the intentions of ourselves (the tech community) while looking at the results of others (eg, the military). But the question we really need to be asking is if our impact on the world leads to better outcomes than theirs, regardless of what either group intended -- and I'm not sure it's so clear cut, once you account for second order effects of social media.
And it's certainly not as simple a moral calculus as "Well, they work on weapons so they're worse people than me!"
While I get why some people don't want to work on things that could potentially be used for evil, the dividing line between good and evil is often a lot blurrier in hindsight than it seems in the moment. Many of the most valuable technologies (see above) have come from the desire to kill people and not be killed in return, while many of the ideas that have killed the most people (communism, Nazism, eugenics, manifest destiny, crusades) have come from the desire to make a more perfect world.
None of these are tech products, so it's apples to oranges.
Additionally, just because most good things have come from military in the past doesn't mean that's the best way to produce good things, now or in general.
We all look back at the Apollo program with a kind of a nostalgic sorrow because many of its achievements have not been surpassed yet. We would be capable if we put the resources into a worthy successor project. But the truth is that Apollo was a cold war project intended as a propaganda campaign against the Soviets. It would never have happened without that conflict (including the Korea, Vietnam and Afghanistan wars).
I've also read the hypothesis that the Apollo project also served as a peaceful demonstration of ICBM capabilities without expending (and revealing actual capabilities of) real ICBMs. Kind of like applying an added layer of assurance in MAD, by demonstrating through technological affinity the missiles aren't duds and the claims of performance not fabrications. If so, then that's one helluva diplomatic gesture for the history books to cover in the future.
I think this continues in US in some degree. US military gets as much money as it wants. Military spends how much money it wants on whatever research it wants.
For me that's the secret weapon of US science. Other countries struggle to allocate any significant portion of the budget to research while in US it's easy because it goes through army under the guise of protecting the country.