Hot glue does come off in the washing machine easily.
It's not recommended to use hot glue on clothing or other fabric that you need to wash in the washing machine because the washing machine will eventually cause the hot glue to lose it's bond on the fabric and then the hot glue will come off in the wash.
Hot glue is good for other fabrics and furniture or anything that doesn't need to go into the washing machine but you should use some other regular fabric glue or sew the fabric when it needs to go into the washing machine.
If you get hot glue on your clothes then it will usually easily just peel off the clothing by hand once it dries.
But even then the hot glue on the fabric should easily come off in the wash as well but you may need to remove it from the washing machine.
That is because the hot glue once washed off of fabric or clothing won't be able to drain through the washing machine.