Here's a different approach -

1. Will a glider rating hurt your resume?
2. Will flying a glider make me a worse pilot?
3. Will I learn nothing from flying gliders?

The answer is 'no' to all questions.

If you haven't added a new rating, qualification, or passed a 121 school in the last couple of years adding a new rating, and exposing yourself to a formal review, might help your resume.