Robert wanted to be a football player or a fireman; he thought they were cool, but never followed through. He wanted something practical. Something that could get him some money easily. He's considered bad because he was withholding information as leverage from Lena and trying to get into her pants. That is pretty shady.
I'm gonna list some of the stuff that would make him an shady / bad guy to some, and why it's not the case. Just from what we have seen so far. He could be written as a serial killer later, but I'm just talking up to what we know about him now.
A lot of people had a dream of a certain job, but they wind up in a different career than they wanted, and it just didn't work out. That's life. That don't' make him bad, in fact it makes him good. Because, he is doing what he has gotta do to take care of business even if it is not his dream job. He doesn't want to be a mooch, and is showing some work ethic there.
As for not telling Lena... He didn't want to tell her at the restaurant. It could cost him his job or problems if he is saying stuff that shouldn't be said yet especially if she has a reaction right then and says something. That is unprofessional. So, he wanted to let her know outside of work.
Bringing up the fact that he saw her insta & stalkfap stuff to Lena... Uh... I guess that could be considered "Creepy", that is one of Lena's optional reactions, but it really depends on how she takes it if it is creepy or not. It's not like he was caught sniffing her underwear like Stan... Her social media things are public. Even Ed mentions commenting on her social media stuff too. I'm pretty sure every guy in the game is looking at her social medias. In fact Perry, and Wade & Ian were all commenting on it as a group together...
I would also argue he is more so a "Good Guy" especially when it comes to the Axel fight... Axel beating his ass. He was sticking up for Lena who was being stalked by a psycho ex.
The Perry / 1st Ian fight right after that... Perry was drunk, and spilled his drink on Robert. Robert was having a bad day and lost his temper and already got beat up by Axel.
The 2nd Ian Fight... He isn't really the "Bad Guy" either... They are both fucking the same woman.
As for him being apprehensive when facing Ian a 3rd time but without a fight when he is on a date with Minerva... They have fought twice already. If you got in a fist fight with a guy 2 times and he shows up at your place of work how are you gonna react?
You could argue, "What about when he gets a blowjob / has sex with Lena at work!" That's very unprofessional, and I'm sure he would get fired, and probably Lena too. However, it's an adult game. I'm sure many guys would bang their hot model coworker if they could at work... Sounds like the dream! You also need to remember it's an adult game and the risk of being caught spices it up.
Lena's cat dislikes him... but it's a cat. Maybe he is just not good with cats? In writing there is a trope of people being a sign of a bad person if animals dislike them. That could be a clue in subtext.
If Lena and Robert hook up then we get Bad Jessica... That's hard to refute as him being a bad person. That also makes Mike bad as he is bad for cheating on his girlfriend, and later on Lena. Mike is obviously a bad guy.
He has flaws, he is not a perfect person by any means, but in terms of how bad of a guy he is. He is far from the worst guy in the game:
Seymour is by far the worst... He is just a ruthless monster. I don't need to make a case against him. Everyone else already has. He is so bad that Emma of all people hates him... She has like 0 hate in her soul. Jeremy is a lying snake that can't be trusted. Axel is a psychotic stalker ex with a short fuse. Stan does creepy stuff like steal underwear to snoof. Ed is married and older than her dad and still hitting on Lena all the fucking time dropping pervy messages on social media and drawing her naked. Wade totally neglects the shit out of Cindy for video games, and does not appreciate her at all. Perry lives off daddy and is a bum, and is just weird in general. Mike cheats on his girlfriend.
Of the guys in the game how is Robert one of the bad ones?