I dont see how the "we are the only ones with a moral dimension" argument has any sway one or the other as to the existence of life. And to be frank, I am not convinced that we are the only species with a sense of moral dimension. I do know this, we are about the only species that kills for the sport, will kill for no reason, and will kill in the name of something we have never seen and have no proof of existence.
The thing that strikes me in these sorts of discussions is that the people peddling them, be they christian, muslim, atheist, whatever, is that they always "know" that they are right, and that the moral high ground belongs to them. You know something....it doesnt. The best that we can do when it comes to questions of morals, is to arrive at some mutually acceptable set of standards and behaviours and then judge according to those standards. All those discussions about freedom of speech, human rights, the right to self determination, the rule of law, respect for others and their beliefs, and above all, tolerance are things that float into my mind when I think of morals. Amongst that general concept is the right to paractice ones religious beliefs without fear.
But none of this discussion has any place in a discussion about the possibility of alien life. We can not know if such ELFs have a sense of morals or not, heck, we cant even know if there is intelligent life out there. If we start bringing some alleged moral or religious code into the debate, then we have taken this enormous step backwards, to somewhere equivalent to the Inquisition. We should simply look at the facts, or even the potential facts, based on verifiable source material, and avoid making judgements based merely on beliefs. Basing decisions on beliefs rather than facts, or observations, reduces our cognition to the level of voodoo basically