You are absolutely right. That is why such an argument is logically invalid.
Which is why I was somewhat surprised to hear them from someone attacking Creationism--by their own lights, they ought to know better ;-)
Not quite the same thing. Creationism is not a scientific idea, and it is reasonable to attack the people who make moral proclamations, if they fail to live up to them.
The difference is that science bases its authority on the objectivity of its observations, the fact that they can be repeated by any competent person. Religions are based on unique events witnessed by a few individuals, and their credibility is essential to the credibility of the claims to truth.
There have been attempts to censor scientific observations based on morality, excluding from publicationfor example, the data compiled by the Germans and Japanese during WWII in their cruel experiments. Such censorship makes sense only if it discourages future cruelty.