I think there needs to be a buffer of a few turns after fighting a war before being able to trigger a trespassing grievance.  It's very frustrating to siege an opponent's city successfully in order to destroy their war support only to be rewarded with giving them several free grievances which they immediately use to bolster their war support again and cause a lot of agro for you.  It doesn't feel like this is working as intended.

And to add, when you take cities from them - now they are trespassing. The game needs to distinguish, if possible, between regular trespassing and this after war period. Agreed.

Yes, the game must add a post-war cooldown feature to prevent endless wars