Not at all, considering Paganism is an umbrella term used to describe different non-abrahamic religions. As others have mentioned, as long as they don't try to tell me my beliefs are wrong then I'm cool with it.
Not unless they think their beliefs are better than mine and belittle me. Because being pagan doesn't mean just one thing!
What Heart_And_Seoul said. It can be insulting when the other Pagan is completely dismissing my views as silly, stupid, a waste of time, or harmful (just because I honor Jotnar alongside the Aesir and Vanir) and not even bothering to listen or attempt cooperative dialogue. But that's it. Otherwise we're all free to have our own beliefs from our own traditions and personal beliefs. Hope that answered your question a bit.
No, why would I? 'Pagan' is a HUGE umbrella term - it encompasses an enormous amount of religious belief, from Egyptian Reconstructionism (Kemet) to Neo-Celtic-Wicca; the former is highly ritualistic and rules-based, the latter is something very free-form and adaptive to the person. It's not 'insulting' - to anyone - when someone believes something else. Kind of a weird question.