This isn't a knock against people who write fics where Jack and Maddie disown Danny due to his powers, but I find them needing to face their prejudice to be more interesting and in character. For all of their faults, Jack and Maddie love their kids and would be willing to risk anything to protect them. I also think that Danny learning that his parents will accept him for who he really is will lead to Danny stressing about one less thing in life since he already has a lot on his plate.
Plus, even if the two accept Danny, there's the story opportunity of Danny helping his parents realize that not all ghosts are bad and that they can research ghosts without hunting and experimenting on them.