Remind others whether bad feng shui at home will affect them.

As long as you really know Feng Shui, of course you can show it to him. If you know a little, it is not necessary! It won't be bad to show people Feng Shui in your home, unless the level is limited. It's not good for you to see what hurts others. If you have the real ability to help others, it will only be good for you, not bad.