I'm lactose intolerant
Oh no! You can't have things like cake?
No, I can't! Why are you being judgmental about this? Do you believe in karma?
It's okay to not want to eat certain foods if you are not able to. However, you should not get angry when people offer food or ask if you can have it, because they are just being considerate.
Eh. I don't get why anyone should be forgiving about this kind of things. I will get mad at them for being intolerant about my lactose intolerance.
Some people are ignorant to what lactose intolerant is. It is better to educate them about it instead of being angry with them. That way they also become more tolerant.