The first question leads immediately to the second question. When one redefines terms, one changes the meanings of the sentences of people used the word.
I believe the my personal freedom stops at my neighbor's door. So, my inclination is to say that I do not have the right to change the meaning of words. I would go further to state that I have an obligation to try to understand the meaning of the words spoken by others.
As I studied classical logic, I realized that logic is more than just the internal process that I use to develop my ideas.
Classical logic gives us the tools to understand others. Because we all have different perspectives on life, we will never share the exact same definitions. But if we strive to understand the definitions used by others, we can have a more complete understanding of others.
Unfortunately, history is full of people who believe that they can confound others and sneak into power by subtly changing definitions. Even worse, there are some intellectuals who like to develop contradictory definitions. When words have contradictory meanings, then dialecticians with clever word play can make sentences mean whatever they want.
Modern logic holds that definitions are in constant flux. Each use of a word changes the meaning of a word. Hegel used the term "sublation" to refer to the process of ever changing definition. Hegel especially loved sublating terms to the point that the terms took on an opposite meaning of the original terms. Hegel presented numerous word games that framed slavery as freedom and freedom slavery.
Modern Logic became popular as a reaction to the US Revolution. Conservatives who wanted to preserve the social order of the ancient regime (including people who wanted to "conserve" slavery) loved Hegelian proofs that slavery was freedom and freedom slavery.
These absurd modern ideologies that keep wreaking havoc started as a Conservative reaction.
Thinkers promoting this new logic came up with carefully parsed and new definitions of "freedom." A great example here is the LDS Church which developed a new term: "Free Agency." The idea behind "free agency" is that the Heavenly Father gave Spirit Babies the ability to make decisions to test the resolve of the spirit babies. You have free agency to join the political hierarchy of the church and follow its commands. Those who do not join the hierarchy and follow its dictates must be cast out.
It actually gets more bizarre. The Book of Mormon appears to most people to be a lie, but it is greatest truth ever told. Believing in something that appears to be a lie hardens Spirit Babies for eternal life in the Heavenly Kingdom.
Young Hegelians, wanting a change in the social order, love using redefined terms and developed "Modern Liberalism" which has people seeking a totalitarian state in a misguided pursuit of freedom.
Conservatives tweak definitions to preserve a social order. Progressives play a game in which words change meaning with each use as they engage in the struggle
The game of changing definitions, however, destroys the ability of people to communicate. A society with political rogues grubbing for power by changing the definition of terms quickly degenerates.
My observation is that this game of changing definitions to obtain power is generally played out in the ruling class. The Middle Class generally wants definitions to stay the same so that they can understand their society and build in a more stable environment.
The game of changing definitions has had a terrible impact on our efforts to defend freedom because different groups have remarkably different definitions of freedom.