Straightedge Catholic....?

Pretending to drink the blood is dishonest. I don't' know if it's a sign of disrespect, but God knows what you're doing. He's more important than the priest. It's okay to decline it. If your priest has a problem with your declination, he's wrong. Discuss the issue with him. If he insists you drink the blood, go to his superior or talk with another priest.