On my family tree other people have added information that is incorrect, and the delete tool will not allow me to delete the people/names that are wrong - HELP. This is very frustrating.
Welcome to the "Community.FamilySearch" Forum.
I am juts another 'lowly' User/Patron ...
Short Answer: One DOES NOT "Delete" incorrect individuals/persons, one SIMPLE "Detaches" them.
Basically, one "Detaches" (or, disassociates) the incorrect individuals/persons from the one's "Ancestral" Lines (ie. from the particular, "Couple"; and/or. "Parent-Child", Relationships).
Here are some "Knowledge Articles" in 'FamilySearch':
I hope this helps.
tl;dr: for Brett's response: you can't delete people in Family Tree, but you can delete relationships.
(Well, technically, profiles can sometimes be deleted, but it's under very limited circumstances: only the person who created the profile has the option, and only if nobody else has ever edited it.)
To reduce the chance of the errors being re-introduced, it's a good idea to contact the person who attached this wrong family to yours, using FS's in-house message system. (Find one of the person's changes, click on his/her name, and choose "Send a message".) Politely inquire about why this person thinks that his/her family belongs with yours, and point out the reasons that it doesn't.
Here is some information on how you can try working with others to decrease errors in the tree:
I like putting a brief comment in the Life Sketch because it is visible on the Person Page without having to click elsewhere to see it.
Here is the link to the knowledge article on how to message other users of FamilySearch as referenced by @Julia Szent-Györgyi: