Welcome. My 10 year old nephew loves to sew, especially on rainy days. Occasionally he asks me if it's ok for boys to sew. I tell him, yes, everything you learn to do makes you more valuable in the world.
That's true for both boys and girls!
Explain to your friends that sewing isn't that different from carpentry. Both sewing and carpentry require precision, geometry skills, concentration and creativity. The big difference is that for carpentry you work with wood and a multitude of tools; for sewing you work with fabrics and a multitude of tools.