Much like Sex & The City, Shameless is full of sexual situations that are generally dramatically productive. It’s not just fun sex where the casual male viewer can tune in for an eyeful of Emmy Rossum naked. Instead, the numerous Ghallagers come of age and come face to face with their own issues through sex. The writers have probed the emotional worlds of their characters by way of thier sexualities, and even when sex is used as comic relief, it serves to draw useful contrasts between different kinds of relationships. The heart of Shameless is its searing, brutal honesty. Its honest depiction of sex and sexuality, in particular, is what’s made the show so entertaining and fascinating for the past six years. And this fact is why one of the plotline’s in last night’s episode left such a sour taste in my mouth.

Last night, Ian Ghallager (Cameron Monaghan) discovered that his boyfriend, Caleb (Jeff Pierre), has been sleeping with his high-school girlfriend Denise. When Ian confronts Caleb about it, Caleb is dismissive. He claims that what he’s doing with Denise isn’t cheating (“sucking another guy’s cock” — that would be cheating). Caleb defends himself, telling Ian that he’s sexually fluid and that he and Denise have been having sex with each other since they were teenagers, and there’s nothing wrong with it. Ian seems unable to wrap his head around the fact that his boyfriend isn’t “100% gay.” Caleb is reasonably shocked at the fact that Ian even thinks such a thing even exists. But Ian is steadfast in his assertion that if Caleb sleeps with women, he’s not gay. He outright rejects the idea that Caleb is bisexual, saying plainly that bisexuality isn’t real. After Ian picks up a woman on the train and gives straight sex a try, he’s convinced of what he already knows: he’s 100% gay, and if his boyfriend is anything less that 100% gay, he simply can’t accept it.

What’s so incredibly frustrating about this plot line is how easily it goes against everything we’ve come to know about Ian’s character. We’ve watched Ian come to terms with his sexuality over the course of the show, and I personally found it hard to believe that he could so quickly become so close-minded. At The AV Club, Myles McNutt suggests that possibly what we’re seeing in Ian’s reaction is an opinion molded by his experiences with Mickey Milkovich — a relationship which might have “pushed him away from understanding sexuality as a spectrum.” But without the necessary dramatic work, the writers completely fail to convince us that this is the case. Instead, Ian’s insistence on this idea of rigid sexuality flies in the face of his other sexual experiences. Kash, the older, married Muslim man Ian was sleeping with early in the show, was clearly not 100% gay. Maybe there’s an argument that, much like Mickey, Kash was forced into a straight relationship and his bisexuality was not genuine but necessary for his own survival. But what about another of Ian’s lovers, Jimmy’s dad Lloyd, who openly declares himself bisexual? Are we to assume that Ian, who worked as a go-go-boy-for-hire in Boystown, has never come into contact with men who sleep with both men and women? And should we forget that we’ve recently seen Ian stand up against these kind of two-dimensional judgments when his boss refused to hire him as an EMT because of his bipolar disorder?

Apparently, this is the breaking point for Ian and Caleb’s relationship. I saw it coming, as once any character on Shameless settles into a happy domesticity, something usually sneaks up to destroy it. But why did the writers choose to make Caleb’s bisexuality the bridge that Ian simply can’t cross? Especially when there’s a more obvious, logical reason that Ian would want to leave Caleb after this episode’s revelations. Caleb was dishonest. No matter how he might try to justify his behavior, Caleb was having a sexual relationship, in secret, with a person who was not his partner. That is cheating. If Caleb’s sexual fluidity was such a fundamental part of his life, then he should have disclosed it to Ian, just as he disclosed his HIV positive status. Ian is right to feel betrayed and hurt. There is nothing wrong with polyamorous, open relationships, but they are arrangements that all the partners involved need to be aware of and must provide their consent.

Instead, what ended up happening in last night’s episode was a blatant reinforcement of tired ideas about bisexuals. Caleb’s nonchalance, his indifference to what is an obvious breach of trust, regurgitates ideas that bisexuals are inherently dishonest. There are ugly stereotypes that suggest bisexuals are greedy, promiscuous and shady, supposedly because they can’t seem to settle on which sex they prefer. Ian’s dismissal of bisexuality wholesale — which, sadly, is a commonly heard sentiment in the LGBTQ community — supports the idea that something like “100% gay” actually exists, and bisexuality is some deviation from a normative sexuality. When Ian and Lip discuss the situation, Lip states that he would rather a girlfriend cheat on him with a woman than another man. Instead of using this moment to do some interesting emotional work, the writers end up turning Lip into a typical straight guy, who sees a woman’s sexual fluidity as non-threatening. All these tired cliches have no place in the Ghallager family unless they’re coming out of Frank’s mouth. For a show that has consistently been progressive in its treatment of both heteronormative and alternative sexualities, this storyline is a disappointment, and one that ultimately does a lot more harm than good. While Shameless doesn’t necessarily have a duty to work against these stereotypes, it does owe its viewers the decency of working through the opinions and beliefs of its characters, especially when they seem to crop up as nothing more than a convenient plot device. By not doing so, the writers commit an offense to the viewers who have invested themselves so deeply in Ian’s character. Put simply, this storyline was lazy, and clearly the product of uninspired writing. Shameless can, and should, do better.