In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; and take the helmet of salvation, and the sword of the Spirit, which is the word of God Ephesians 6:16–17, ESV
I have noticed that some of those who should be contending earnestly for the faith spend way too much time either defending themselves from these sorts of attacks or they are being consumed with nit picking with others to the point of distraction. I am in no way suggesting that all professing Christians should be automatically considered our brethren, however, if the faith of a brother or sister in Christ is solidly grounded in Gospel of our Lord Jesus Christ, justification by faith alone, and Sola Scriptura, then I am most certainly not going to contend with them over things that the Bible does not make clear enough for that. We must contend for the essentials, the non-negotiable parts of our faith only. On the other hand ecumenicalism is always out there and ready for us to make the foolish mistake to compromise.