Dissatisfaction is a gateway to disputings which is translated "doubting" in the Greek language, however, in this verse it is referring to profitless "disputings" (or arguments) with our fellow men, in relation to whom we are called on to be "blameless and harmless" (vs.15). These disputings often flows from vainglory (2:3). "Do nothing out of selfish ambition or vain conceit. Rather, in humility value others above yourselves..." (NIV)
As Children of God we must treat each other with love in whatever we do and refrain from vain glory. Your view may not be agreeable with the majority, or your way of doing something may differ from my way... but that does not make us any more less than each other...nor does it distinguish us as loser verses winner. No! So why beat down the preacher's (or whoever) reputation and waste your grumbling over the way they do things. Don't allow the devil to destroy your relationship with your brothers and sisters (in Christ) over some disputing. Show love and respect.
Consider the consequence! Grumbling is a sin. God hates sin and sin it will only pull you away from God, never towards Him.
I came upon this song and thought it was very interesting. So true... but sad.