I voted remove links and let people know.
Though thats only if you actually caught them. 9 out of 10 times sponsors are called out for shaving theres not a scrap of proof and its either the webmaster's lack of knowledge, or just a 'feeling'.
I have only ever caught 1 sponsor shaving outright, and that was silvercash not crediting my referral joins several years back. I was able to get sales data from my only referral (krusty) and only around 50% of the joins were being credited to me

Emailed them and they credited the missing refs.