You know something nutty, not directed at you, where you have no opinion or stake aside from sleeping next to them. 
Something where you don’t agree with them, don’t think it matters one bit, and are preemptively exhausted from the effort and time it is going to take up.
They decide they are going to fight city hall, or change homeowner bylaws to allow neon penguins as a lawn ornament, whatever something like that.
Be as supportive as you can without necessarily encouraging the crazy, I guess. If it’s that important to your spouse, then you should show you care, even if you don’t agree.
Smile and nod. She puts up with my stupid-assed shit; to humor her in one of her quioxitic episodes is the least I can do.
I’m sure that the sane and stolid group we know Dopers to be would never have spouses prone to nuttiness.
(I mean, c’mon, in a household with a Doper in it, it’s an easy bet where the nuttiness will be coming from.)
This, Hey she puts up with way more then I do. I support her in the minor stuff. She supports me in my minor stuff. It is a partnership, so no big deal.
It strongly depends on how much involvement they expect from me.
That’s pretty much the definition of a spousal relationship, isn’t it? Putting up with each others’ nuttiness without judgement. They put up with ours, so we put up with theirs.
Whenever my GF dresses up our dog as a jack-o-lantern, a Santa Claus, or a Thanksgiving pilgrim, I just give him a sympathetic eye-roll implying, “Yeah, old buddy; I have to sleep with her too. Just grin and bear it.”
I usually just roll my eyes and say “I take no responsibility…”
I was divorced 25 years ago and I still cringed when I read your post. I somehow felt like I should have been more supportive about all these perceived threats and enemies. No advice from me. I tend to try and ignore, it doesn’t work.
Be as supportive as you can BUT you still need to be honest about your position.
Not quite the example you’re looking for but one I’m willing to share is related to the current power outage.
When the tempurature in the house started dropping and we started talking about going somewhere else to stay my husband was determined to stay at the house. I accepted that until we dropped to 10 degrees at which point we discussed why he wanted to stay (safety of the house, freezing pipes, intruding on someone else’s christmas) and dealt with each one.
If I had just taken him at his word the dogs, kid and I would have been safely at a friends house leaving him to shiver in the house by himself. Not a happy solution for any of us.