A couple days ago, a tenant was backing up and hit my dad. The tenant did not come out the car until we told him to. He was extremely rude and said it was all my dad's fault since he was behind his car. However, his injuries aren't life-threatening and he's fine. We are thinking we should sue the tenant and kick him out, although he doesn't have that much money.
So should we just kick him out or/and sue him?
A broken leg is not "life-threatening" but would still be an injury with damages that should be paid.
If the tenant has car insurance, your father should obtain the insurance information from the tenant and file a claim.
If the tenant does not have car insurance, the tenant likely is in violation of WA's mandatory insurance law that requires a vehicle's operator to have at least the statutory minimum level of liability coverage. The tenant's driver's license will be suspended if he causes damages and does not have at least the required minimum coverage.
A driver has a duty to take care to not run the driver's vehicle into another person or object. Unless your father suddenly jumped into the car's path, the tenant likely is liable for not checking that the way was clear for the tenant to move his vehicle.
Your father should review the specific facts with his attorney to find out his legal options.
If your dad is fine what would you expect to receive in a lawsuit? Personal injury claims compensate someone injured on the basis of the nature and extent of the injury caused and any other damages caused by the negligence such as medical expense, wage loss, etc. From what you describe your father has none of these injuries. You mention that the tenant does not have much money? Based on what happened to your dad would the jury award your dad anything? You say the tenant was rude? A jury would not award money because he was rude?
Does he pay his rent on time? Aside from being rude in this situation does he cause any problems. I assume he has a lease? What would be the basis under that lease for "kicking him out." I doubt rudeness is mentioned in your lease. If he is otherwise a good tenant--pays his rent and on time and does not cause any other problems, I would want to keep a tenant like that.
As to suing, it depends on what you mean by "fine." The description "not life-threatening" leaves a lot of wiggle room.
As to kicking him out, in Seattle you must have just cause - even if he is month-to-month.
Consult an attorney familiar with both areas of law, and provide more details (but do not provide them online).