Hitler was defeated by being nice to him
In that sense you're right- some people only understand and respect force, and the only way to stop them is to use force against them. The analogy of Hitler might be compared to hardened criminals- being nice to a criminal won't stop them from victimizing you.
This is a different battle though. The small % of racists who want to burn minorities' houses down, they must be met with force.
Force doesn't win hearts and minds though. Force is intertwined with fear- 'if you do xxx, force will be used against you'. So it might stop some church burnings, but it doesn't stop racism. Force doesn't win 'hearts and minds'. Force doesn't convince a racist that they were wrong. It might make them too afraid to speak up, but it doesn't win them over, and they will only take their message underground, where it will thrive.
You are confusing the spread of ideology with the spread of a conquistadorial government. Remember, most of the Germans who supported Hitler didn't realize the Jews were being massacred. And we didn't go to war to stop Nazi ideology, we went to war to stop Germany from conquering the entire fucking world through military means.
The problem with using force to stop an ideology is that to the people who might follow that ideology, the fact that you care enough to use force against a belief system must mean there is something important in that belief system they should be checking out. Trying to stop an ideology with force only makes that ideology stronger, gives it validation.
If you want to stop an ideology, ridicule it. Make fun of those who believe in it. Talk about how stupid they are. Talk about how they are morons not worth your time. Don't give that ideology the validation of deserving force.
The other problem with violence, is it prevents dialogue. If you are hitting somebody while talking to them, they are not going to hear what you are saying.