I don't know that we are all entitled to have an opinion about everything; I refrain from forming them about things where I'm ignorant and I think that is the wisest way to go -- at least I try to not form them and certainly don't say them out loud.  Often of course I just follow the experts -- they are useful that way so long as one is aware of possible vested interests.

As far as to whether aliens exist or not and if they do what they might be like, I think we are all ignorant and are therefore better off keeping out mouths shut.  However, since we are all on fairly the same level, I suppose wild-ass guesses don't hurt so long as we don't get too committed to them.

My guess is that they don't exist, at least in any form and distance we are ever likely to understand and actually encounter.  Otherwise they would long since have been here, and they aren't.  There are in addition to that rational difficulties that have been pointed out in the evolution of such beings that would seem to imply they are going to be incredibly rare.  My guess since of course the probability factors are at this point pretty wild-ass and may kick us hard some day.

In a few centuries I trust we will have a much better handle on things.  What if it turns out we really are alone?  What conclusion would it be appropriate for us to draw from such a conclusion?  The conclusion might be, "Oh, wow, we have a deep responsibility here to preserve life and spread it to the rest of the universe."  Nonsense.