If someone is dyed-in-the-wool, or has dyed-in-the-wool opinions, they hold those opinions strongly and will not change them.

He's a dyed-in-the-wool traditionalist where cooking is concerned - he doesn't allow any modern gadgets in the kitchen. 在烹饪方面他是个彻头彻尾的传统主义者——他不使用任何现代厨房炊具。