It's Tommy we are talking about, not Rusty. For me Tommy wouldn't care if something that is shameful or negative for others is being associated to him, like him having STDs, him being poor, him being an asshole etc Every single one of these he would dismiss and ignore, it does not bother him nor does it hit him.
But being sentimental? Being less of a raging asshole? Maybe being seen as someone vulnerable and/or caring? He would hate it. He hated it during the whole game when the MC tried being considerate of his feelings, always saying that "He don't to care for his fucking feelings so much". That's basically the only thing I can see Tommy being ashamed of being... being more human, just like Quinn and just like Lily.
Ok, so first of all. I think the line "Don't care about my feelings that much, I'm not a girl" was more used as a jab to MC than anything else but if you think otherwise is up to you. It's not like people are going to make fun of him for being sentimental, hell most of the DIKS are a bunch of softies (Rusty cries with Cathy, there's the whole Jaime and Leon drama on Halloween, MC is a fucking wuss regardless of the choices you make he is just either a bad snowflake with a potty mouth or a regular snowflake, Derek is always moping over Ashley, etc.).
Which is why he is trying to hide it, duh. Because he don't want people to think he is wuss or even more human for having fucking feelings. It wouldn't feel like a cop-out because that's the most Tommy thing to do, trying to hide that you are human too.
Like, for example, he is clearly bothered and shaken because Heather left him, he didn't try to make the christmas party more about him and wasn't loud and obnoxious as he was during Hallowen. Every single one of the DIKs sees this, but he is still playing it off like he does not give a fuck.
I think you are misenterpriting my argument. I didn't said that Tommy would care if people find out about his addiction or not. I said he would care if people knew the depths of it. We are not talking here about a mere I need to smoke once in a while, we are talking about a guy that if he doesn't smoke periodically often he gets angrier than usual and he is already prompt to having a short temper. The code might be there for him to not have to explain shit if he needs a fix in an emergency and for him to have free reing to take money if he needs it for anything else, he can just say it's the DIK code and just take it as we know Rusty won't do jack squat and MC won't even question why things are not accounted for.
Here's what we know,
1- We know that Tommy is a serial addict (Not only with Pot but he injects shit heroine? maybe or some DPC made up drug)
2- We know that Tommy took money from the safe that was meant for the Halloween party budget and we "assume" he returned it afterwards at some point but we don't know for certain
3- We know that shortly before Halloween he met with Vinny to buy from him (Most likely using what he borrowed from the safe since we know his prizes were higher than Quinn's at that point).
With all this evidence, It seems more likely to me that Tommy has had addiction problems for a while now and it just has gotten worse with time.