Rufus developer here.
First of all, Rufus tries to prominently display the partitions it is going to delete, with two major prompts, one asking for confirmation that you really want to erase the drive (with that prompt mentioning ALL the partitions that Windows can see, and not just the first one) and a second prompt, whenever multiple partitions are detected, that tells you that Rufus has detected more than one partition and asking you whether you really want to delete a drive that contains multiple partitions.
In other words, you get two very prominent prompts allowing you to cancel the operation before Rufus does anything, so it's hard to see where your "without my permission" comes from, as Rufus asks you for it twice if your drive contains more than one partition, and at least once if there's only one partition. So please be mindful about misrepresenting what Rufus does (which can be very easily validated), when it was very much designed to always ask for user permission before repartitioning a drive.
Now, with regards to your underlying question, what you are seeking to do (partition preservation) is not a feature that we plan to ever provide in Rufus. This is detailed in the FAQ here as well as here. So if you want to preserve one of the partition of your drive, I will respectfully ask that you use a different utility.
On the other hand, if what you are interested in is adding persistence for a Linux "Live" image, please note that we do have an enhancement request for that, which is low priority, but which we plan to complete eventually... Once this feature is implemented, you will still not be able to preserve partitions, but you will be able to allocate some space, in the form of a persistent partition.