Pam in answer to your list (all good concerns to raise - privacy, not falling prey to guilt by association - definitely stuff that should be avoided) I'd say here's why we should be worried.
(In what follows I am reluctantly sticking to MN's guidelines about pronouns, because I want this point to stand, not be deleted on a technicality).
Back in November 2016 the local branch of Gay Pride (I think it was) suspended David Challenor pending the results of the court case. At that time Aimee Challenor was a trustee of the that local branch. Aimee's mother was also plastering her facebook with "David is innocent" posts. So for Aimee to claim now that in 2017 when she used David as election agent she had no idea that he was awaiting trial for charges of rape of a 10 year old, when Aimee was a trustee of Pride, and shared the same house as her mother and father, certainly stretches my credulity.
Secondly there's the issue of what Aimee has been involved in in her own right as a person forming Green party policy.
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She and David jointly worked on terfblocker, while the Challenor family residence was listed as the official local address of the Green party - and held all the membership records. That is a serious conflict of interests.
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She and David worked on youth policy including the recommended "affirmation only, don't tell the parents" model which drives a horse and cart through good safeguarding practice. If Aimee had any ability to learn from this debacle, at this point she would be distancing herself from this policy at this point - but as far as I know she is not.
These points - about possible dishonesty, dubious choice of election agent, data protection, and safeguarding policy - are why the Lib Dems should not be touching this person with a barge-pole.