I just voted the Europa question one up ... Besides, I am with Paul (his comment below the question here). I do not understand the different receptions, too. Imagination and the thought of alien life forms is what drives this business, if it is about exploration beyond LEO. If I propose a mission and say, "hey, I'll investigate a few rocks", the proposal has a high risk of being turned down. However, if I propose a mission and say "hey, we are looking at the rocks for signs of life", people look differently at it and the chances for funding are much much higher. This is real-life space exploration. Like it or not, but the search for alien life is part of the show and part of being human.
We have to allow those questions. Otherwise, we should remind our politicians plus all the reviewers of proposals and tell them to be more careful with what the approve funding for. But ironically, how do you justify a mission flying to a dead celestial body in the general public? You just do not. (The Moon may be the only rather strange exception to this rule.) It will always be about life, officially, in one way or another, no matter what happens behind the curtain.
EDIT: I was once talking to a journalist. He told me that most of his colleagues thus most newspapers will never ever pick up a story about a space exploration mission towards other planets, moons or asteroids unless any statement on alien life (bacteria is just fine nowadays) is involved. In a similar way, medical studies are reduced to 'what does it mean for our love life', geoscientific studies are reduced to 'when will the world end' ... the list goes on. Well, some stuff is reduced to money - space exploration is expensive, which always generates negative yet high impact news. Personally, I hate this attitude in the media. But it accounts for a lot of the mentioned questions, in one way or another. It emphasizes, why we need to handle them - by giving answers instead of closing them.