opinions are fine. You don't think it looks like a yellowbelly? by all means say so. Don't pull punches - offer a clean critique and your complete, constructive list of thoughts on the matter.
Filling a critique with "crappy" "ugly", whatever, is just not necessary. It adds nothing to the thread. You can get your point across all the same without being rude with "That doesn't look much like a YB to me..." or something similar - with the added bonus of not making anyone feel abused, or worse, insulting an innocent animal.
I'm not sure I saw any insults coming from you, but there certainly were some nasty responses that couldn't really be justified.