I commented earlier on this; but I didn't get around to responding to the original topic. I do have to agree with Edward's assertion that the question is really more of a personal one than a general one. To posit that naturists are either passionate or obsessed is akin to saying 'gamblers are addicted or talented.' An individual can be one, both or neither.

Approach this from a slightly different angle. The outsider has no authority - nor do they have the specific knowledge - necessary to make an accurate assessment of a naturist (nudist). If you have no earthly idea why someone is involved in a certain lifestyle how can you possibly presume to know their inner convictions in the matter?

So we can summarily dismiss them from the equation. No outsiders here.  All that's left then, is the worldwide community of lovers of nudity in all its legitimate forms; and the proper responses are pretty much found heretofore in this forum. Personally, I don't think there is anything in this life worthy of becoming obsessed over; obsession usually leads to harm. One might argue that some of the greatest inventions and discoveries of mankind have been reached by someone with an obsession. Ok, granted... but how many of those people had normal lives or relationships otherwise? 
Passion?  Well there's a big word. In most cases passion eventually manifests in uncontrolled outbursts, demonstrations of unbridled emotion, some of life's more sober responsibilities going neglected.  Passion is a word better used to convey a feeling than being allowed a foothold in the life.
All things are lawful to me; but not all things are expedient. I'm naked when I can be and I avoid being naked when it would cause offensive misunderstanding in another or otherwise be physically harmful to me to be so.

There is no worldly undertaking, whether it be in commerce, entertainment, recreation, art or any other endeavor, that cannot be harmed, and sometimes destructively so, by the rule of obsession or passion; both emotions common to mankind, yet both only attractive when in a muzzle and on a leash.

Having only just read this, it bring it back to me when I became more open about naturism. I did't go around telling people as I was a bit scared of the reaction, but without boring everyone with the details I did a nude protest photo against the Royal Mail when I worked for them when we were in dispute with them. I got a lot if ribbing and mickey taking for a while but it enabled to be open about naturism. My family have known for years but not wanted to do it themselves. I have realized most people don't care as long as you do not force it on them.

Wise words Steven. 

I think it's just sort of who I am, like being a husband and father.