Yes, there is a whole subsection of the internet that seems to think that vegetables are a net negative. They site doctors that suggest that fiber causes irritation in individuals with compromised intestines (leaky gut syndrome, etc.). It's exhausting having conversations with them as a vegetarian as they seem to think the only healthy way to eat is bone broth, butter, mct oil, and meat.
It’s common for someone in a flare of an IBD to be unable to eat vegetables without irritation. You should seek to understand the root cause of an individual’s experience instead of invalidating their experience due to your own.
If they become healthier then they should be able to increase vegetable intake which will further increase their health.