There's no wrong way to say a Reese's?

So many of you have heard about this debate already. Let me catch the others up to speed. People in Larissa's home town pronounce Reese's, Reesie's. It's something I used to tease her about and she mentioned it to Brittany and Ryan. Brittany said, "So what." I said "Larissa is saying it wrong, it should be said Reese's." This started a long and heated debate. Brittany said you can't say wrong or right, only standard or not standard-common or uncommon. Let me back up, to
The ironic begining: The Reese's debate began because Brittany and Ryan had been discussing the proper (more common) way to say tyrannical and asked our oppinion.
I agree that some words have more than one way for pronunciation. And sometimes there is a more common way to say a word but both ways are correct. Brittany said because this town in Ohio all say Reesie's that is right for them (colloqualism) and therefore I cannot say they are saying it wrong. In that area that's how it is said and it doesn't change the meaning. Good point but I must disagree. First let me say I understand Brittany's studies are in this area and she is more knowledgeable about some grammatical topics than myself and others. Let's put that aside considering this topic isn't of such great depth that others can't have an opinion or say on the subject. Please in your comments make a more valid point other than saying Tom is stupid and Brittany is the expert in this area, I know this may be a tempting argument for say Chris or Phil. Ok, as stated before I agree that langauge changes over time and we have to be sensitive to the different accents and or dialects of our fellow countrymen. We are not discussing other langauges or the english language in 50 years. The debate is, can you say someone is pronouncing a word wrong or right. On a philisophical level it is probably true that nothing is definite or wrong or right. But such arguments are seriously missing the mark. During this debate much has been argued and talked about, I will try to present my argument with two main points.
1) The candy is named after the man called Reese:
Do we have the liberty to change this man's last name because it's applied to a candy? Or does the pronunciation of his name stay in tact because the candy is named after him? I submitt that we cannot decide to say his name however we choose (well I guess we can do what ever we want) it is his name and we don't tell him how to say it. Are we to believe our simple brothers and sisters from Ohio will call this man H. Reesie? Of course not. Why does his name change because we add 'S to Reese. If our name was spelled with an "E" and we made a Clarke bar (I know Clark bar already exist) called Clarke's bar would anyone say Clarkie's bar? Some people probably, but would it not be incorrect if our name is not pronounced Clarkie?
2) The 'S show a possessive quality. IE, if you were to say "Look, there is Mr. Reese's car." Almost nobody would say Reesie's car. Larissa readily admitts she would say Reese's not Reesie's car. What's the difference between his car and his, shall we say buttrecups or pieces?
There are other points to debate and argue but this entry is already long. I know we've hardly scratched the surface, but tell me what you think. Is there no wrong or right way to say any word? Can we say words however we want but not last names? Do we not follow rules when speaking and writing (I know I don't when typing, please no comments)? What would things truly be like if everyone pronounced words however they felt like and we accepted that as correct english rather than accepting these words or phrases as colloqualisms?
An ironic end: Brittany said Ryan spelled ridiculous incorrectly (rediculous). Ryan a usually good speller said "No way you say it rediculous." Brittany chided him with a correction, "Ryan it's pronounced, ridiculous." But to me this whole debate his recockulous because that's just how decide I say it.