I must say, I totally agree, that autism symptom related posts should be allowed and even required to have the autism-spectrum tag on them. Even if someone has not autism but is aware of having some autism specific traits in a given context, it isn't important in such case, if that person actually has diagnosed autism or not. If that's the kind of solution someone is looking for, let them just tag it as such. Its not our job to evaluate how useful such an answer would be, if that's what being asked for.
And if someone still feels an urge to challenge this assumption, the way to do it would be writing a full frame-challenge as answer, rather than removing the tag.
A little background from my personal experience.
I figured about possibly having Aspergers like 6 years ago. But it took me like 5 years till my therapist finally was convinced enough to diagnose me.
In that time I myself wasn't really certain if I would have autism or it would just be like my therapist kept saying "There is a significant amount of Aspergers related symptoms influencing me, but under the line that not being enough impact for giving a diagnose." So there were a lot of things I had trouble with being typical for autists (cause as I know now, I am an autist). But back then I wasn't really sure about it and always hesitated calling myself an autist before I had the diagnosis, cause despite I felt like one, technically I felt like lying, calling myself one without having the diagnose. If I had back then made a post here and had to fight for the relevance of the autism tag to my post (well, I created that tag, so in my case it would have been more the fighting for the tag's right to exist, but anyways), I would clearly have felt very discouraged by that and also that would have had negative impact on my journey to fighting for the diagnose. So I absolutely agree and think, if someone wants to have that tag on their OP, should rarely if ever be changed by the community.