You don't have to modify the model to parrot your opinion. You just have to put your stuff into the system prompt.

You can even modify the system prompt on the fly depending on e.g. the user account or the specific user input. That way you can modify the responses for a far bigger subject range: whenever a keyword of a specific subject is detected, the fitting system prompt is loaded, so you don't have to trash your system prompt full of off-topic information.

This is so trivially simple to do that even a junior dev should be able to wrap something like that around an existing LLM.

Edit: In fact, that's exactly how all these customized ChatGPT versions work.