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?
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."