Scientists do not question the concept of science
Questioning the validity of science is precisely how science is done These are 2 different statements, pertaining to 2 different actions.
Both the statements are true.. err... alright, maybe not the first one as much. You can question the concept of science (which, in a way, boils down to "Question everything") and still be a scientist.
Questioning the validity of (other's and your own previous) science is a part of the concept of science.
Questioning the concept of science is more of a philosophical matter and would be valid in a quest for better concepts.
The above two statements are not actually denying each other.
Lookie here! This thread has 8 parallel lines.