Starting a conversation with "Please don't take this the wrong way" or "I hope this doesn't upset you" doesn't mean that you can then go on to be cruel, insensitive or intolerant. It just means that really you know you are about to make a wrong decision but haven't bothered to find an alternative.
Now it is likely that I am preaching to the choir. I am not writing this for the other parents of children with special needs who have seen their children be politely excluded from play dates and apologetically not invited to birthday parties. I am writing to those other parents. The ones who seem to have forgotten that their job is to teach their childen about diversity, tolerance and problem solving skills.
So for those parents, let me make a few suggestions.
If your child says "I don't want Bobby coming to my party because I don't want to worry about him acting weird", try to find out what the actual concern is. Is there a specific triggering behavior that you could prepare Bobby for? Maybe you could suggest that Bobby's mother stay nearby in case there is a problem. Maybe you could remind your child that there will be plenty of other children at the party and not to focus on Bobby. Maybe you could remind your child of the positive characteristics of Bobby and that the world is made up of all types of people. We don't have to like them all but we need to be tolerant of them. If this is a child that you would otherwise invite, a family friend's child, a neighbor or a classmate, then you should expect your child to include this one. The best way to teach your child tolerance is to model it yourself. Help them problem solve a way to make the party work for all the kids invited as well as your own guest if honor.
If your child says I don't want to play with Sally anymore, again try to find out why. Does your daughter think that Sally is boring, stupid, selfish, or some other characteristic that may be challenging because of Sally's disability? Help her to see that this behavior is not intended to be malicious but rather that Sally may need help learning to be a good friend. Maybe you could suggest alternate activities that they could enjoy. Try taking them to a neutral place such as a park or a movie. Maybe in a new environment Sally might be interested in new ideas or possibly in a neutral territory you could consider a situation where she doesn't have to share.
Ultimately if you want your child to grow up being not only tolerant but inclusive then you need to expect that from the very beginning. Don't expect them to learn these values as adults if you haven't encouraged it of them as children.
Here are a few more suggestions for encouraging tolerance and inclusion:
1. Encourage your child to include children with disabilities, to play. If the child cannot play the same as other kids, come up with creative ways to accommodate the child's challenges. Making up games can be lots of fun
2. Teach the golden rule; Treat others the way you would want to be treated.
3. Help your child find commonality -- a hobby or interest -- between him and this child with disabilities.
4. Don't label the child with special needs. Referring to other child as "that child with hearing aids" or "the girl who stutters" only points out differences, issues that may not even concern your child. Use "people first" language.
5. Empower your child. Let them know that they are allowed to feel safe and valued in a friendship as well. They should not accept being physically or emotionally attacked by a child with special needs just because the child has a disability. Nor should they feel like they always have to do what the other child wants if it is not a mutual choice.