Lying for an agenda is foolish. It always comes back to bite you in the ass. Those that lie to promote their agenda personal or otherwise are shortsighted and cant see the forest though the trees. The truth no matter how painful is ALWAYS useful.
The tricky widget is KNOWING the truth. Being able to tell fact from fiction that's a gift that not all people have and most to varying degrees. Ones mans truth is another mans lie. Even facts can lie. Discerning what is and is not is a lifetime endeavor never perfected.
For me it is always better to tell the truth as I see it regardless the personal pain to myself and those around me. Its much simpler to deal with. It also makes dealing with being wrong about certain truths easier. It boils down to the golden rule and karma for me. Do unto others as you would have them do unto you. What goes around, comes around.