That is an extremely serious charge to make against another Christian. The teacher who is accused of such a heinous act of deception would have to be teaching actual heresy. We haven't seen anything published against Rick Warren that shows such is the case. 

Also, having never endorsed Rick Warren's methods, we aren't accountable to defend them. We do see that he is succeeding in presenting the Gospel and the message that Christians should live for God and not for themselves. We do not believe that every church should try to implement his ideas on church growth.

The Apostle Paul wrote this about others who were preaching the Gospel;

"Some, to be sure, are preaching Christ even from envy and strife, but some also from good will; the latter do it out of love, knowing that I am appointed for the defense of the gospel; the former proclaim Christ out of selfish ambition rather than from pure motives, thinking to cause me distress in my imprisonment.

What then? Only that in every way, whether in pretense or in truth, Christ is proclaimed; and in this I rejoice."  (Phil 1:15-18)

And he also writes in Romans 14:4;  

"Who are you to judge the servant of another? To his own master he stands or falls; and he will stand , for the Lord is able to make him stand."

Certainly, things could change with Warren's ministry in the future, but from what we've read and seen so far, we do not feel it's our place to condemn him.