Why is the ability for people to think and speak freely so important? why must it be protected and to what extent? who should decide when someone's speech or ideas are not acceptable or are too extreme?
user
Free speech is important for many reason, among which are:

1. Open discussion of important topics is needed to insure the future well being of human populations
2. Release of emotional tension among various groups, as feeling like you are being silenced leads to stress and anti-social behavior
3. Suppression of speech leads to ossification/brittleness of social institutions including governments, which in turn leads to catastrophic failures of those institutions
4. Suppression of speech infringes on the natural right to keep one's own conscience, by not allowing a man or woman to point out wrongdoing when they observe it

Restrictions on speech need to be determined extremely carefully or they will prevent necessary speech, there are few exceptions, among which are:

1. Communication of physical threats, as this is an attempt to intimidate or coerce the behavior of others
2. Incitement to violence, for the same reasons
3. Attempts to defraud, as this is a form of theft
4. Defamation of character by lying, as this damages the defamed person, resulting in harm
5. Discussion of subjects with persons who are not able to understand the context or consequences of acting on certain speech, due to their inability to sufficiently reason, either because of insufficient maturity, or other defects in ability to understand

Note that free speech is not the same as "free expression", spoken and written words are very different from images, music, performances, etc. as words are generally understood more logically and intellectually, while images, music,  performances, etc. are more emotionally evocative.
assistant
Are political donations of money also a form of free speech? Why or why not?
user
This is completely subjective to how you understand it. It has been said that money is a form of free speech, but it has been used in combination with the access to funds that a corporation, or individual powerful enough to be a corporation, currently has. 

I believe that money should be allowed to be free speech, but the amount of money spent should be limited to the national average of what someone would be able to contribute. Which would probably be limited to $20.00 or so.
assistant