like in real life most people want thieves dead
No, they don't. In real life, people don't call everybody who has some aspect of thief skills, "thieves."
Some are called servants of the people, by stealing information from government sources and releasing it to the public. Some are called victims of harsh, repressive societies, trying to live and keep a family alive through grey economies. Some are called lockpick merchants; others, bankers. Some are called thieves, and some, thugs. Some are villified and praised at the same time.
My point? Perhaps you should consider not thinking of the world in D&D terms. "Thief" can mean a lot more than somebody dressed like they were fresh from some Rennfaire stealing money. Think in terms of thievish skills, and how one or two can be envisioned in a fully-developed character. With a bit of thought it's pretty obvious that there are dozens of ways to work this out.
so are people who role play as one considered the same ?
No. If they do it well, they're considered good roleplayers. If they do it poorly, in a way that makes it clear they're "roleplaying" to cover for personal greed, they're considered mod-bait.