I am fairly certain that I've explained this to you before, but as tabula rasa appears to have struck again...
ID must stand or fall as a scientific theory on its own merits. Science knows of no such thing as a default explanation to be fallen back on once other explanations have been disproved. Therefore ID must explain the existing data concerning the history of life on earth (all of it that we have, such as the retroviral evidence, not just cherry-picked fragments), make testable predictions about what we are likely to find in the future, and be subject to being falsified by hypothetical observations. No-one has ever explained how ID can do this (to me anyway).
How many times do I have to say that ID seriously questions the merits of evolution because life at exists today simply cannot be the result of random chance. If not random chance, some other force must be behind the design of life as it exists.