The word ‘but’ is more damaging than it looks when used in a discussion. Agreeing with someone and then saying ‘but’, may completely undermine your efforts to be understanding and agreeable. Those three letters somehow have an ability to kill everything good that you said before it.
Instead try the following example:

“I agree with your point, but I have some concerns”

…and consider using this instead

“I agree with your point. Here are my concerns.”

In writing, they may look similiar, but verbally, it makes all the difference in the world. By omitting the word ‘but’ you help make the other person feel less defensive, and more responsive towards your own opinions.