My suggestion is to move on. When you have prospects with brush issues in California and Travelers and Hartford (two of the more liberal preferred carriers with brush issues) are declining, but State Farm, Farmers and/or AAA or USAA are saying yes, then you're not ever going to win.
You can beat your head against the wall all you wish, but those direct carriers have made strategic decisions to take those kinds of risks and absorb the potential losses (and there ultimately will be losses) in order to gain market share. There's probably a sound underwriting message when so many carriers say no, but I can appreciate the fact that doesn't put any money in your pocket, but there are times in insurance sales where you shake your head in amazement and just move on. Let it go. Find other prospects. Get on with your business life.