If this was a multiple foul, you could say :
"You'll want the roughing the passer penalty as it awards you a first down."- except in this situation where 1st & 5 becomes better than 1st & 10.
If the coach was bellyaching that DPI is no longer an awarded first down, he would probably joint a large group of
that feel the same way. You could say :
"Coach, BY RULE, pass interference is no longer an awarded first down. I don't write the rules, I only enforce them."
....if he continues to rant....
"Coach, you may want to get a job in the NFL where not only is it an awarded first down ,but also a spot foul."