Being supply chain professional company's interest comes first, but many often have to act as supplier's advocate. How to manage such circumstances?

This is a real life delima, there couple of reason behind it like

• We have to do this becuase we always want to develop our vendors as our strategic partners which ties us with them emotionally.
• There will be many instance in which they had given you favor in your short comings in return you advocate your supplier but this thing is done until companies interest is not on stake.
• Interest of employee, company and supplier are same so employee advocate their supplier by knowing this only
• Sometimes management & supplier don't know their importance so purchaser would have to advocate them becasue of his importance or USP