Where the Roman people offended at being compared to dogs by Scipio? Was the suggestion of the need of collar offensive? The collar is a real thing:
Varro says this:
To protect them from being wounded by wild beasts, collars are placed on them — the so‑called melium, that is, a belt around the neck made of stout leather with nails having heads; under the nail heads there is sewed a piece of soft leather, to prevent the hard iron from injuring the neck. The reason for this is that if a wolf or other beast has been wounded by these nails, this makes the other dogs also, which do not have the collar, safe.