Coal was also considered clean in the beginning because they didn't have to sacrifice forests anymore.
We may not consider the waste a problem now, but that may very well look differently in 50 or 100 years.
Again: I am completely fine considering nuclear power as one of the best options we have. I am not so fine pretending it's without tradeoffs, because that would ignore how any other form of energy generation in the past/ever finally turned out.