Why are people saying Lee opposed secession and slavery when he risked his life and the lives of his men to defend them?

Lee was not personally in favor of leaving the union as were many others. He, by the principles of the time for any general, treated Virginia (border state) as his home and had to support the decisions of the Commonwealth. In his words “If the Union is dissolved, and the Government disrupted, I shall return to my native State and share the miseries of my people, and save in defence will draw my sword on none”. He basically said that if there are two sides wanting to kill each other, he will return to Virginia and defend it from any party that wish to do it harm.

He did, undoubtedly, take passive stance on slavery and made general arguments in favor of slavery while condemning it as a universal "moral and political evil". To say otherwise would be historically inaccurate.

Overall, Robert E. Lee defended his homeland Virginia and was operating under their decisions.

He did oppose slavery and secession. He was actually Lincoln's first choice to lead the Union Army but Lee declined. Lee refused to fight against his home state of Virginia and joined the Confederacy when Virginia voted to secede.

He risked his life to defend his home, Virginia.

Revisionist history.

Ironic that they are being attacked by other revisionist historians.

Leave the history alone. Whether you like the Confederacy, as some do, or do not, as I do not

He fought for his home state. It is in the history books. You should read one instead of listening to the MSM.