“For I am Yahweh your God. Sanctify yourselves therefore, and be you holy; for I am holy: neither shall you defile yourselves with any manner of creeping thing which moves on the earth.”
Let them consider with Whom they have to do. He is ‘Yahweh their God'. Compare Exodus 20:2. This is their covenant God speaking. Thus they are to sanctify themselves, to ‘make themselves holy' by separating themselves to God. As His people they are to set themselves apart to God and His service and not be scrabbling among the unpleasant things of this world. His desire is that their thoughts may be positive and pleasant and not negative.
This is not forbidding the sensible study of such creatures, but forbidding a misuse of them by eating them without discrimination and being involved in what is low.