Is touching a small amount of impurity intentionally excused according to Shaykh al-Islam Ibn Taymiyyah, such as one who intentionally contaminates himself with a drop of urine or intentionally kills an insect on his clothes?

Slight impurities are excused if it is difficult to guard against them. This is the view held by Sheikh al-Islam Ibn Taymiyyah, such as mouse droppings in food, street mud, stable dust, and splatters from a butcher's blood or a wounded person's blood. What is meant by "slight" is what is considered slight عرفًا (customarily), but this does not apply to someone who deliberately contaminates themselves with impurities.