I think you are being very loose in your terminology when you say we have the technology. What you have said is that we have a source of fuel which has the potential to get something very heavy an increadibly long distance and that it has gone through a degree of testing. But whether this technology would suffice for propulsion has yet to be determined, it hasn't even been tested out in the correct environment yet.
What we certainly don't have is a background in sending anything living on a long journey and back again in one piece. We don't know whether it would be feasible to send one person or whether multiple people would go. We don't know how much room they would need, how they would cope with the length of the flight, whether there would be any long term issues related to S.A.D. or any number of other physical and psychological health questions. As previously, Mir has scratched the surface, but that is all.
In short, we don't even have the full scope of the problem yet, so how can we possibly have the technology?
I agree with your stand on nuclear power. It does have a stigma associated with it which is perhaps unfair and perhaps borne of ignorance and sensationalism. I would not go as far as to suggest that there would be no danger just because we propose to use it in space though. When playing with fire (and I believe Chenobyl proves that we are playing with fire) a healthy degree of caution is wise whether it is in your own back yard or not.