OP,
Your parents sound awful and I would absolutely say your upbringing has massively caused, if not contributed to your anxiety.
@Natty13's post is excellent.
Your parents are rude and disrespectful, and in your place I would see very very little of them and take some space to give you time to really think.
Are you discussing your childhood in therapy? You should be.
Particularly as your sister feels similarly.
The chemicals on the grass is dreadful, of course you were right to be concerned.
I think they are extremely controlling and belittling of you, and their actions are intentionally upsetting you, as they see you as a child not deserving of consideration or respect.
Your mental health is very precious and you must mind it.
You do not feel these elevated levels of stress around friends and in other situations, your parents are the key triggers for you.
I do not think speaking to them again about this serves any purpose.
See a lot less of them and perhaps they will join the dots.
Spend time with people whom don't stress you.
With people so dismissive of you and your feelings, you do not owe them a relationship with you or your child.
Can you imagine them correcting and undermining you as you parent your child?
If so, even more reason to step back.
Perhaps if you step away from them they might find a bit of kindness and courtesy towards you, or not.
Either way, you really dont have to and shouldn't, IMO, tolerate this.