The difference is that we can find concrete evidence through SETI, but not through ID.
Our of curiousity, what is the "concrete evidence" that points to extraterrestrial intelligence?
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there is the kicker.
there is no "concrete evidence"
similiarly atheists will say : show me your concrete evidence for God. (But exclude everything in the natural universe as evidence of a creator.)
It's like saying, "Show me the forest, but don't use the trees as evidence."