NO, using wool is not cruel.
Sheep either shed their wool and it can then be gathered for human use,or they are shorn one or twice a year for health reasons and the wool then becomes
something the sheep doesn't need any more and humans are free to use.
Wool is widely used in clothing from knitwear such as socks and jumpers to cloth used for suits and costumes. It is used in the furniture trade both for making chair covers and for upholstery. Wool is usually specified for garments for firefighters.
Every wool fiber has a natural elasticity and wave or crimp that allows it to be stretched as much as one-third and then spring back into place. Its complex cellular structure also enables it to absorb moisture vapor, but repel liquid. No synthetic fiber has been able to combine all of these characteristics.
Wool is comfortable to wear in both warm and cool climates. This is because wool is an absorbent fiber. When the air is cool and damp, wool absorbs moisture and keeps a layer of dry insulating air next to the skin. When it is warm, that same absorbtion capacity takes up perspiration and keeps insulating dry air next to the skin, making the body's natural cooling system work better.
Wool Fiber diameter varies by breeds of sheep and is used to determine the purpose of the wool. Wool made up of smaller diameter fibers or fine wool is used for clothing while wool made up of larger diameter fibers or coarse wool is used for carpets and rugs.