Motivating someone to do something that is good in their lives is not a sin ,it just adds balance to one's life.
I have noticed and read the way some are blasting these aspects of ways,you know mankind always talk but they don't think about consequences.
There is a struggle going on in this world against good and evil,right and wrong and the positive and negative aspects of these ways always come into view.
And what motivational speakers are merely doing is trying to caused an effect stir in the struggle, so why blast these motivational individuals for their useful efforts.
Children,youth,and grown men and women struggle each day with issues and some of them may not have the resources,funds or persons in their lives to get the help needed for the struggle that may have occurred.
And here is where motivational aspects can be applied,the person may be ready to give up on life and just by passing a motivational poster that reads"Never Give Up" might be the perfect answer of direction needed to challenged the caused of the struggle in the person's life.
Motivational aspects how ever way they come were put here for a reson and that is to help emphasized a changed in someone's life that seemed to be struggling. 
I believe in helping others and that is the way in which I was born into this world and for those who seemed to worry so hard about motivational aspects and why it is here .
Well all I can say is that they also seems to have a struggle in their lives because they are against a method that is good,relevant and helpful and the remedy for critics struggle is to get some sort of inspiration in some kind of motivational, yes the same methods that you blast.
Individuals out there say that they counsel people and I don't think that they would go out there and tell these struggling individuals to go out and try to make their problems worst,"No!
As one would try to help in what way they can to help these individuals, as sometimes it may not be in person but a word of some kind of enlightenment could help and also impact on a caused as to try to help someone that need help with their struggle.
Any motivational aspects is not a sin these ways are just trying to help someone as they guide them in as to help balanced one's life as "Words of Movement"
To go on a path of helpfulness, strength and self worth that is needed to help individuals understand that these ways were also put to give them a helping hand.
And all made by individuals who understand the hurt in these struggling individuals lives and who are willing and trying to help in ways of these motivational directed lines.
So to all good and motivational aspects and the people behind them I say continue to voice and get the work done.
Continue to push and help the ones in need don't ever worry about the criticism and critic's because they are the ones that have much envy,struggles and greed.
Motivational methods are used as stepping stones as to help others get up and not continue to fall.
As to gained courage and strength and try to put their lives back in order as to make they lives better.
As to you the critics out there I will continue writing because know that my words of motivational aspects will impact in someone's life as to help them unto a better directional course.
And yes critics I always know what your criticism is about as "Criticism do not fulfill the body it weakens the core".
What I can tell you is that this  seed will  not weaken because it was planted by a wise ,loving and caring planter with protection in mind against all eroding aspects of contaminates from you the critics, this seed bears fruit that is sharp like a two edge sword.