Many Boomer managers resent millennial workers for asking for quick promotions or raises without having paid the same dues as they had to.
However, resenting them for asking in the first place greatly reduces your credibility as a manager. Now you're acting out emotionally instead of taking the role of a leader and explaining in a logical way the reason they may not deserve, or be ready for the raise or the promotion. They won’t resent you if you treat them with respect instead of resentment.
Challenging yourself as a leader to keep personal feelings in check, (no matter how well founded) will pay long-term dividends with the people that you manage.