Firstly, r14 is not to low for a r20 behest. Eight r14s could probably finish a behest, even with all the mobs that come with an 8-person behest.

Secondly, anyone up to r24 gets bonus sp from the r14 person (the r14 person only gets bonus sp from people r19 or lower). You're a r23 con (assuming your forum name = your in-game name). You're getting bonus sp from him, he's not getting bonus sp from you. If there's anyone that should be complaining, it's him.