So just don't. Not even to defend assaults or accusations. Quotes become misattributed and you don't want your good name posted under tangled threads. Go out of your way to be congenial and helpful to your competition. Now I'm sending them business.
Self employment is often feast or famine.
A strong referral network of aligned professionals can help even out the work load. Make it worth other professional's time to send business your way. Consider how time consuming marketing and searching for leads can be. Referrals are pure gold. Banners The web offers endless opportunities for free advertising.