A major constraint in the way of preaching is the fear of public opinion .Some times a person feels discouraged due to opinions of people so he gives up preaching to get rid of public opposition.
He/She should bear this thing in mind that public opinion cannot degrade a person who loves Allah and Rasool salal laho aliehi wasalam and if some one will turn back Allah swt will bring another group of people who are not afraid of blames and allegations of people as mentioned in the Holy Quran:
O you who believe! Whoever from among you turns back from his religion (Islâm), Allâh will bring a people whom He will love and they will love Him; humble towards the believers, stern towards the disbelievers, fighting in the Way of Allâh, and never afraid of the blame of the blamers. That is the Grace of Allâh which He bestows on whom He wills. And Allâh is AllSufficient for His creatures' needs, AllKnower. (Al-Ma'idah 5:54)