I totally agree and I think it's kind of laughable to call Jasper Lapis' abuser when Jasper was clearly the victim!
Like you said Jasper didn't coerce Lapis into fusing, Jasper tried to convince her to fuse and Lapis agreed when there was no need to do it to defeat Jasper. On the beach Jasper knew she had lost, Garnet had already beaten her, the ship was destroyed and now she faced Garnet, Amethyst, Pearl AND Rose (from her point of view). This is why she wanted to fuse in the first place and if Lapis had said no that would have been it, with the ocean right there Lapis alone could have probably one shotted Jasper, she posed no real threat in that moment.
I don't understand why so many people view Lapis as a poor victim of Jasper when Lapis herself acknowledges the awfulness of what she did! She trapped Jasper in a fusion and then abused her until she liked it. Before this Jasper considered fusion a short term battle tactic (which isn't wrong looking at how the rubies use it), after her experience as Malachite Jasper now craves fusion but has a completely warped sense of what it's supposed to be like and Lapis is responsible for that.
Jasper deserves to be healed from corruption and when it comes to her possible redemption no one should give a rat's ass about Lapis' feelings in that matter.
Errr...huh?
No.
Lapis wasn't some sweet little defenseless damsel with no agency in the matter.
She willingly fused with Jasper in order to torture and control her; she mentally abused this gem for months at the bottom of a deep dark ocean, holding her against her will all while taking a sadistic pleasure in the whole ordeal. She could've said "no" on the beach and helped the CGs quadrupedal team a weakened Jasper, but nope. All she wanted was to enact her petty revenge scheme.
Her motives for trapping Jasper were mostly selfish, hateful, and vindictive. Saving Steven (and only Steven. Not his friends, not his home, or his family. None of the other things he loved) was an after thought.
I mean...Lapis pretty much admits to all of this in Alone at Sea, she recognizes how awful she is for missing the ability to slap Jasper around and chip away at her sanity.
She misses being able to be another gem's cage; she misses being able to dominate another living being.
That was the big important internal conflict of the episode for goodness sake, her coming to grips with this and admitting it to Steven (which he annoyingly glosses over for no good reason...).
With all this in mind, How in the world is Jasper some irredeemable abusive monster who shouldn't be given a chance? Why do Jasper's awful deeds count as uniquely evil but Lapis' don't?
The worse she ever did to Lapis was grab her arm a couple of times and throw her in jail for being an unabashed liar on a sensitive mission.
Yes, Lapis enjoyed hurting Jasper.
Usually, people aren't 100 percent victims or abusers. That's true and that's what Alone at Sea gets at. But what is the context?
The context is that Lapis enjoyed hurting the high-ranking and physically powerful gem who wanted to hurt her friend, threatened her, wanted to report her to the totalitarian authorities, and yes, coerced her into fusion. Physically restraining the person is coercion. I don't feel sorry for Jasper in that context or her sob story about her dead dictator mommy and the immoral regime she oversaw.
Secondly, it is far from clear that Jasper was defeated when the ship crashed. She was weakened, sure. But remember that Garnet herself barely beat her before; all three CGs failed when Jasper first arrived. Why couldn't that happen again? After all, Jasper appears to be a legendary soldier to HW. Jasper as a gem species is built to fight. Even if it was possible for all four of them to take Jasper down, that presented some uncertainty that was diminished by Lapis acting covertly. You don't have to have perfectly pure reasons to do something good. Lapis protected her friend and got some revenge on someone who kidnapped her and tried to violate her. There may have been other resolutions to the conflict that were possible. But what happened to Jasper must be put into context by what she did to Lapis and what she tried to do to the CGs (which, by the way, includes attempting to shatter Amethyst after poofing her in Crack the Whip).
I'm not saying that being attacked gives you carte blanche to do whatever you want to the people you perceive that injured you. But what Lapis did is hardly unreasonable given the situation and given what happened to her.
That is all enough to call into question whether the CGs should give her a chance, especially given Lapis' experience. If Steven does try to give Jasper a chance, as is likely to happen because Steven remains naive, I would hope that Lapis intervenes. Perhaps Jasper should be repoofed and rebubbled or Lapis should attempt to shatter her. Maybe there are more creative solutions like harnessing Jasper's power to power a gem artifact.
The point being that in bringing these other gems into his family, Steven should take care to respect their feelings too, even if they clash with his ideals. There is no reason that he should be the one deciding the fate of all these gems. Governance should be shared. In the absence of any formal rules or process, I hope Lapis and those gems that sympathize with her defend her interests.