Is having a preference for a husband (when seeking one) of your own descent ruled as discrimination?
No, this is not ruled as discrimination because a woman could need to marry someone with same background in order not to feel any inferiority towards him. The Scholars say that same descent is not a condition for the validity of marriage, yet a woman has the right to look for someone with same (or almost same) family background because this husband will have rights over her in bed and she might not be able to tolerate him as a husband (intercourse) if he is from a different background.
Yet, although it is allowed for a Muslim woman to look for a same descent husband, Islam does not differentiate between people according to families.
A Muslim woman should respect the street cleaner and she should not think that she is better than him in any way. Yet she will find it difficult to marry him and live with him as his wife.