How can I "Heed them not"?

Hello everyone.
Recently I have felt quite... upset, so to say, about the blatant mockery and disinformation about our church online. My faith is not at stake, but recently a dear friend of the church came across some anti (Polygamy, BoM translation methods, you know, the usual crap antis love to use) and while I am helping him stand firm, I also feel angry.
How can I follow what Lehi taught in his tree of life vision? How do you recommend I "heed not" all the "mOrMoNs ArE NoT ChRisTiAnS" thing?

Thank you in advance, and sorry if the post appears offensive.