Sole Prop loans are always a fun challenge. You don't monitor use of the funds and must go on the clients word. Most times it's used for both personal and business use, it's the nature of the game.
Consumer deals are less risky than small business deals, hence the easier pricing. Lenders should choose the PRODUCT that the client asks for, not the best priced deal. The bank needs to enforce this and require that small business loans and lines are booked as small business. Consumer are booked as consumer.
If this client came in for a small business line and the lender chose a consumer line, he chose to provide a product the client did not ask for. He exposed the bank to rate risk and data integrity risk. Encourage him to understand that consumer products are for consumers!!! You price your products differently for a reason. He needs to support the bank he works for by offering the appropriate product based on the clients stated need prior to documenting.
Think in the worst case scenario...you book 1,000,000 tiny sole proprietorship loans as consumer. (You do this because your clients figured out you're not as smart as the rest of the banks in town so they apply with you and tell your friends). How is your data integrity exam going to go when the examiners look at the files? And...how in the heck are you going to survive an economic downturn in the small business market that you couldn't even plan for, what with not knowing the full extent of your portfolio in the small business arena?
Oh then there's the Call Report...But we won't go there

Messy jail terms, etc...so difficult to sell to the president when he asks why this was allowed and all...