Can my uncle be deported even though he's been in this country 17 years, has payed his taxes every year and is a hard worker?

He can absolutely be deported as he is here illegally. You need to be speaking to a qualified immigration lawyer who is also experienced handling deportation cases. The $100 you will spend on a consultation fee will be important for you to know if there is anything that you can do for him.
Be prepared to answer these questions and have documents available.
How did he enter the country? Did he enter illegally or did he come in with a visa and then overstay?
Was he ever married to a USC or permanent resident? Does he have USC kids? And is so, how old are they? If they are in school, what are their activities and their grades?
Did anyone ever file an immigrant petition for him and what ever happened to it?
If he has been here for 17 years and can show extreme hardship to usc's- then he may be granted cancellation of removal. You must be able to show how the USC relatives, (preferably spouse, children, parents will suffer if he is deported.
There will be several factors involved in the final decision, but these are some of the basic questions that will need to be asked.

That questions that Ms. Black poses for you to have answer are very useful. We both agree that you should schedule an appointment with an experienced immigration attorney. You should review with the attorney to determine whether your uncle can qualify to file for relief in the form of cancellation. Perhaps, there are other possibilities, but it is unclear. The fact that he has paid his taxes and is a hard worker, alone, will not make a difference.

One thing that I noticed, the main element that your uncle must show is "exceptional and extremely unusual hardship" to a U.S. Citizen or permanent resident child, parent, or spouse to the satisfaction of an immigration judge. This, among other minor discretionary considerations, must be proven to qualify for non-LPR Cancellation. In addition, he must be able to prove that he was physically present in the U.S. for more than ten years before his removal case started.

The above is general information not meant to be legal advice. We strongly recommend that your family schedule an appointment with a competent and experienced immigration attorney.