I don't give anyone clothing unless I know very very well what they want to wear and know their size. Like my teenaged son will wear black t-shirts and anything that says "Metallica" on it. :)
Is this clothing coming from someone you love? If you can't get them to stop sending it through polite hints, and if you can't redirect their giving, just grin and bear it and donate the clothing somewhere. Or why not fly over and spend the holiday with them next year, and sort out what people do and don't like? If you want to wound them deeply, then pull one of the stunts recommended above (i.e., sending it back to them).