Bugs, worms, and to some extent vermin are forms that astral parasites would take (or however you’d conceptualise them, maybe pathological thought currents, or unwanted epigenetic expressions), so there is a reason people don’t go hugging a great big bug - they are also the form negative energy commonly takes when removed in a shamanic healing session, that and unnatural and distasteful things, like fish with teeth.
A scarab would mean a different thing to a guy in Egypt 3000 years back, but today, it’s mainly just a beetle, so unless someone feels very certain they have the right animal for them, most people teaching Harner’s methods will suggest leaving it alone - the spirit animal energy can take any form, so it’s not innately “biased” to refuse something that seems to be taking forms you dislike.
There are ways to handle this if a person ONLY returns stating their SA turned up as a thing that were troubled by, but that’s a little beyond the scope of this reply.
On the rest, I’m going to copy a section from the tutorial I have created on core shamanic journeying regarding this, it in some ways echoes what you’re saying, though to be honest I don’t get my frillies in a twist if people want to externalise their spirit animal, I mean, I did that intentionally with my Personal Daemon and that’s been nothing but awesome ever since then:
Don’t try to guess what your animal is or will be, and don’t be disappointed if it’s not something “cool.”
… It’s perfectly normal to want to have some symbol of it in your life, don’t go wacky and get it tattooed or anything, but it’s fine to draw it, or print out a picture of an animal of that same type, or even buy a piece of jewellery or a t-shirt or something that represents it and becomes a focal point.
It may merge with you later on, or change into a different type of animal, all things are possible - but this is stage 1.
But in a world where friends can turn out to be backstabbers, where “jobs for life” are a thing of the past, so your colleagues today in any corporate job will be the competition for the next gig, is it really a big deal if someone gets an archetypal wolf, and loves the hell out of it so much that they go full “Three Wolf Moon” on the iconography? 
There are far worse affiliations someone can have than to their idealised nature, externalised as a wise and loving guide.