Why money should be in gold? A response of TDM's opinion

I read this article. I quote what TDM has said through the article.
"Backing currency with gold does not make it Islamic, former prime minister Tun Dr Mahathir Mohamad said on Tuesday. He said it became Islamic only if transaction in the currency did not involve interest or riba. "It is not the name that is important. It is the gold backing for the currency, whatever may be its name," he said in a keynote address at the Global Islamic Finance Forum 2010 here.He said there were repeated suggestions for the use of gold dinars, and Muslims bankers must not be moved by sentiments alone.He said people needed also to be conscious that gold prices could change and its value in different countries would differ."If we use gold as a currency domestically, the purchasing power will differ with different countries. Besides that, its bulk makes it unsuitable as currency for everyday use," he said.
There is a time to support him. But this time i don't think so. I would like to come up these questions so that people could aware why this time i disagree with him.
1. Does fiat money carries interest? Absolutely. That's why money should be in gold.
2. You go to the bank, borrow RM100, do they allow you to pay back RM100? Absolutely can't. That's why money should be in gold.
3. Are we feel safer to carry 1 kijang emas or RM4,000 in your pocket? For me, surely i will carry an a ounce of gold. It's just a size of 50 cents coin. Still not practical?. I suggest this.
4.Gold prices change every day thus make them unsuitable as currency? Gold price changes because we measure them in fiat money. Gold prices will not be changed frequently if the measurement of gold is not in fiat money. The gold price should be freed from any fiat money measurement. I know it's impossible for time being but to say that gold prices are changing every day because of gold itself is not really true. The true is because the influence of world currencies that also changes.
5. The changes of gold price bring about the good things. It eliminate the power of manipulation in few hands thus make individuals greater in determining prices and it should be like this in the real economy.