Quite an odd thing to say. While it can be easy to think that someone looks alike due to the "overall appearance" of their faces, closer inspection usually sets things apart. Their completely different chins are one example.

Secondly, his DNA didn't match the missing person's database, which you are getting your "match" from.

There's no reason to be defensive. You've done nothing wrong. Wrong starts only if it is impossible for one to accept that one's theory might not be correct. That can ultimately end in throwing off the real investigation, if one were aggressive enough.