Kindness matters, and kids who see kindness not just directed at them, but acts of kindness that they witness second-hand, have fewer signs of anxiety and other issues.
But, as in most things, some groups are much more likely to see kindness and support directed at them, while others, especially minority and LGBTQ kids generally don’t see kindness around them as often.
Seems to me that is a simple fix for this. Work at being kind to everyone. It clearly matters to kids, and even though this study doesn’t show it, I would bet it matters to adults as well!