Baron Von StarBlade said:
No insult is taken but if you look at pg 14 of the Monster Manual under the creatures with character levels sub heading, it states to use the Monster as Races rules for giving character classes to a monster. Therefore if you want to give a creature character levels then doing so is a variant rule.

The section you're referencing says this:
"If a creature acquires a character class, it follows the rules for multiclassing described on pages 55-56 in the Player's Handbook. The creature's character level equals the number of class levels it has, plus the total Hit Dice for such beings. For example, an ogre normally has 4 HD. If it picks up one barbarian level, it becomes a 5th-level character: 1st-level Barbarian/4th-level ogre (its "monster class") and adds 1d12 to its hit point total. Creatures with 1 or fewer HD use only their character levels (see Monsters as Races, page 22 in the Dungeon Master's Guide, for details). "
The bold text is my emphasis. This pretty clearly points out that the Monsters as Races rule only comes into effect when the monster has 1 or less HD.