Healthy but fatty. I know that doesn't make sense, let me explain. While nuts have a lot of healthy fats, which we recommend generally, they still have a good amount of those fats, so even a few handfuls of nuts can be several hundred calories. Doing this regularly may cause you to gain weight. Pay attention to your portion sizes and it should be fine.
No. With everybody able to write anything they want on the internet, and people imagining that dietary restrictions for anyone should apply to everyone, there's no wonder that somebody's telling you these are "unhealthy", and perhaps someone else calling them a "superfood". It's almost all fiction. Unless your physician has given you directions here, enjoy your life and what you eat.