system
Given the following post, respond as if you're commenting on Reddit:
human
CMV: It's human to feel insecure if your bisexual partner more often than not fantasizes about or desires intimate relations with the gender you aren't.

I would say this fleeting or consistent insecurity would arise for other scenarios too, not just bisexual. For example, if you're a purple woman, and your partner only watches teal women porn. Or let's say you two are open, and they only introduce teal women into the fold. It suggests, that no matter how hard you try, you can never satisfy their desires for traits you physically don't have and will never have. (My personal belief is that that is okay tbh). 

I bring this up because I am bi and I notice many bi people get immediately offended if other people have these concerns.  

inb4: Well, if you're a woman dating a man and he cheats on you with other women, it's the same. Sort of, but really. If he cheats on me with other men nearly exclusively, it's clear it's because intimacy with men offers/satisfies something for him that I as a woman will never and can never provide. 

I don't want to project, but I even noticed with myself, that when I'm dating a man, my sexual cravings outside of him are almost expressly toward women. And that when I'm dating a woman, my sexual cravings outside of her are almost expressly toward men. I've chatted with many other bi people and they relate to the above. 

**TLDR**: It's similar to a straight person being in a relationship and being tempted by other people of the opposite sex, but it's not 1:1. There's a level of "huh, I'll never be able to compete with that desire tbh" that the SO may feel when it comes to the experiences I mention in the title and first paragraph.
gpt
I'd suggest that this is just a rationale to justify how unique your feelings are and to make it somehow not just plain ole' vanilla jealousy.  

Fantasies are just that.  People have rape fantasies, but that shouldn't be an indication that deep down they are dissatisfied with _not raping_.  Fantasy is a unique and distinct category in our lives, it's not the driving force for future decisions.  They do - of course - sometimes line up, but for the most part they don't.  People don't really want to have sex with the step sisters and step-moms, don't actually want to see their partner fuck horses.  The problem here is that you can imagine it - it's not a horse, it's just another person.  But...that the object of the fantasy isn't absurd to you doesn't make it any less a fantasy .

I think you can be insecure to whatever degree it makes you insecure, but unless you have reason to believe that your partner isn't fulfilled by _you_ then fantasy is fantasy and it deserves and equal treatment regardless of whether it's of the same sex, gender, species, etc.