Actually, there is evidence that Google is evading taxes. Whether it would stand up in court or not is another thing, but it looked bad when the MPs griled Google at a public hearing recently.
They are pretending that UK sales are taking place in Ireland, a lower tax jurisdiction, and then in Ireland they are saying they must pay Royalty payments to Bermuda, an even lower tax jurisdiction.
The FT reports that UK sales represent 10% of global sales, so the UK generates $4.9 billion of revenue but Google only pays $70 million corporation tax on that, an effective tax rate of 0.3%!!!
Actually, there is evidence of people accusing Google of evading taxes but until they are found guilty of it, they are not evading taxes. Since you yourself admit you have no idea if the accusation would stand up in court then you cannot say that they are in fact evading taxes.
The MP can grandstand in front of an audience grilling Google in a public hearing every day, it means nothing. If the MP is so sure they are breaking the law, then charge them and take them to court over it. Otherwise, it's just posturing for people who like the drama of accusing large companies of keeping the little guy down by using special versions of the law that supposedly only they have access to.
Some people see a bad company, I see a bad law. A company following a bad law does not necessarily make for a bad company.
Obviously Google isn't evading taxes. Google has lawyers and accountants telling them that this is legal.
But some of the schemes that big companies are using are not legal, and the only way to test that is in court or to hope they agree and pay up.
This is a small argument in favour of tax simplification. The UK tax regime is baffling, and simplifying it would be a good thing.
{EDIT: I say UK tax system, I assume the same is true for the US tax system too.}