More and more research are proving what we always thought: negative experiences are more easily remembered than positive ones. They are also usually more vivid memories.
This comes from a primal instinct: remember how bad your encounter with a tiger was so that you can live longer.
You need to keep it in mind and put the emphasis on positive benefits of what you are selling. There should be enough of them to overcome any negativity towards it.
Please note this is likely to require more convincing than you think!