How is Ian much worse? He has guilt over the Cindy and Emma situation and there will be consequences for Ian once Wade and Perry find out. Oh, and you conveniently forgot to mention that Lena sucks off Jeremy (Ian's friend). Someone he's been friends with for years, not someone he just met and formed a bond with. Lena fucks him as well. Telling Jeremy to keep it secret. She not only betrayed Ian, but Louise with that. Also, Lena isn't the only one that has been hurt by cheating, that's how Ian and Gillian broke up. She cheated on him.
So yes, this is all hypocrisy from Lena and the way she acts. It would be fine, but she doesn't even realize it in her own internal thoughts. It is truly sociopathic. None of us that are bringing this up are upset with the content, just with the fact it's hypocrisy and there is no way for Ian to express any of this. Ian can be disappointed that Lena slept with Robert, but he still forgives her even if he didn't sleep with anyone but Lena. Meanwhile, she can break it off with Ian if he defends himself from Robert. All the power between the two rests with Lena. She decides if they stay together, if she's upset over something she can end it. Ian, well, he just has to deal with her screwing Robert or anyone else for that matter. It's only going to get worse unless outlets for Ian are provided. I mean, he needs to be able to tell slut Lena to fuck off, and break up with her.