Problem:
Filtering User Posts for Foul Language using Toolset form

Solution:
There is no native solution available to check for foul words.

But a possible workaround would be using the Toolset Form's hook: cred_before_save_data
=> https://toolset.com/documentation/programmer-reference/cred-api/#cred_before_save_data

You can make a list of foul words and check against the submitted content and if found remove those words and then assign the filtered content to the field.

Relevant Documentation:
Following links may help you to build such filter:
- https://www.hashbangcode.com/article/simple-swear-filter-php