I write it off because it is electrorally unimportant. Were it a major force, I would view it as extremely dangerous. Remember the last time the USA was isolationist? Bad things happened. VERY bad things. That should never, ever happen again.
Well, you either recognize we have one or you don't - writing it off as unimportant is different. Don't lie. Just say we would need a better one.
There's a difference between isolationist and non-interventionist. There's a post where I explain it(and my own position as well) in the 'Individual Politics' section, you can't miss it. EDIT - I'll save you a trip:
https://uselectionatlas.org/FORUM/index.php?board=14;action=display;threadid=8997Also, do take into account that even if the Libertarians come into power they won't completely dominate. There will always be opposition, so things couldn't go too far(especially since, unlike some other political philosophies that could be considered dangerous, ours isn't tyrannical). It's not as if conservatives and left-liberals would just drop off the face of the Earth.