Any way to make auto discount for patreons?

Basically the title and maybe add them to a coupon whitelist.

At the moment, not. But you could use custom code or another plugin to add them to a list in case they have a patreon_user_id meta.

Okay and is there a way I can access patreon emails from Patreon to add them to a coupon?

Any patron who logged into your site should have the email already at your site. But if you need to access the emails of other patrons who did not log into your site, you will have to write custom code to pull all your campaign.

You can also use some custom code to add any user with a patreon_user_id user meta (in wp_users) to a coupon. That should accomplish the same.