Since I am a Graphic Designer transitioning towards UX Design, I think I have some interesting insights with regard to this matter.
First of all, I've seen some answers talking about explaining them that UX is important. Good point, but we have to keep in mind one thing:
Graphic Designers already know that UX is important. They do not understand precisely why, because they don't have a solid background within this field. They find it very technical, that is why it kind of scares them and, since they won't put that effort into learning more about it, they will say it's boring, as a self-defense measure. Or else, they would think they could be considered too stupid for understanding UX principles.
In reality, the problem is somewhere in the middle. Generally speaking, you don't consider boring the things you understand. When you understand something, you want to find out more about it, especially when it propels towards your career.
However, UX practitioners have to admit that there's a certain terminological mess whithin their field, starting from the very definitions to the job roles themselves (some will say that titles like UX/UI Designer is an abuse, what's the difference between a Product Manager and a UX Designer, and so on).
There are little wars and fractions carried along the theoretical foundations of UX as a field, so when somebody new wants to discover what UX is all about, that person discovers a battlefield. Because the Graphic Designer won't understand much, s/he will blame herself/himself as not being capable. Instead of admiting this anxiety, s/he will say:
"Ok, that's boring" (subtext: It's not that I don't understand it. I don't want to, Ok?")
Returning to the idea of explaining them that UX is important... What we should actually do is make them understand from one look, so they can gain confidence.
Show them an article where everything is well explained and accounted for:
How to Change Your Career from Graphic Design to UX Design
If they have time, maybe they can also take some online courses.
Even if you are a well-versed UX professional, consider that you are not a teacher, so you might explain things a bit wrong, which is enough to make someone lose interest because of the sensible context.
You have to plan your way towards your Graphic Designer, but fortunately there are many resources out there which can help by explaining UX in relation with Graphic Design.
Even so, it might not work. Human motivation is complex. For example, somebody might understand very well the web-flow difficulties which appear when loading that animation, but might not care. Maybe the only thing that matters for them is adding that animation to their portfolio at all costs. I'm just saying that this could happen as well, so it's not something pertaining to being a Graphic Designer. It's something pertaining to being human and having your own hidden motivations. Lots of possibilities...