I would choose a topic like: "Lack of religious tolerance by Christians".

I would use a style of research that was safe. The safest style would be surveys in Eugene, and observation anywhere else. You can't exactly walk up to a Christian in your hometown, and ask them how tolerant they are of Paganism, Buddhism, or any other such religion. I myself have walked the streets of cities, and had Christians come up to me, telling me to turn back from the religion I follow, for it will lead me to Satan himself.

I would post surveys in places, or towns where I knew there was enough diversity so that I wouldn't have my own well being, or the well being of help threatened. I would observe very, very, unobtrusively Christians and gatherings there of.

You would have to deal with lying, and deceiving Christians, and their brethren. That could be a heavy moral weight, and it could backfire. I would do as said above, and be unobtrusive, say as little as possible, and keep clear of any direct confrontation.