All religions have one common ideal, worship of the Lord, and all of them proclaim that there is but one God. This one God accepts your devotion irrespective of the manner of your worship, whether it is according to this or that religion. So there is no need to abandon the religion of your birth and embrace another.
The temple, the church, the mosque, the vihara may be different from one another. The idol or the symbol in them may not also be the same and the rites performed in them may be different. But the Paramatman who wants to grace the worshipper, whatever be his faith, is the same. The different religions have taken shape according to the customs peculiar to the countries in which they originated and according to the differences in the mental outlook of the people inhabiting them. The goal of all religions is to lead people to the same Paramatman according to the different attributes of the devotees concerned. So there is no need for people to change over to another faith. Converts demean not only the religion of their birth but also the one to which they convert. Indeed they do demean God.
"A man leaves the religion of his birth because he thinks there is something wanting in it," so you may think. 'Why does the Svaamigal say then that the convert demeans the new religion that he embraces? " I will tell you why. Is it not because they think that God is not the same in all religions that people embrace a new faith? By doing so, they see God in a reduced form, don't they? They presumably believe that the God of the religion of their birth is useless and jump to another faith. But do they believe that the God of their new religion is a universal God? No. No. If they did there would be no need for any change of faith. Why do people embrace a new faith? Is it not because that the continuance in the religion of their birth would mean a denial of the blessings of the God of the new faith to which they are attracted? This means that they place limitations on their new religion as well as on its God. When they convert to a new religion, apparently out of respect for it, they indeed dishonour it.
One big difference between Hinduism and other faiths is that it does not proclaim that it alone shows the path to liberation. Our Vedic religion alone has not practiced conversion and the reason for it is that our forefathers were well aware that all religions are nothing but different paths to realise the one and only Paramatman. The Vedas proclaim: "The wise speak of the One Truth by different names. " Sri Krsna says in the Gita: "In whatever way or form a man worships me, I increase his faith and make him firm and steady in that worship. " And says one of the Azhvars: "Avaravar tamatamadu tarivari vahaivahai avaravar iraiyavar". This is the reason why the Hindus have not practiced- like adherents of other religions- proselytisation and religious persecution. Nor have they waged anything like the crusades or jehads.
Our long history is sufficient proof of this. All historians accept the fact of our religious tolerance. They observe that, an empire like Srivijaya was established in the East, people there accepted our culture and our way of life willingly, not because they were imposed on them by force. They further remark that Hinduism spread through trade and not through force.
In my opinion the Vedic religion was once prevalent all over the world. Certain ruins and relics found in various regions of the planet attest to this fact. Even historians who disagree with my view concede that in the past people in many lands accepted Indian culture and the way of life willingly and not on account of any force on our part.
All religions that practice conversion employ a certain ritual. For instance, there is baptism in Christianity. Hinduism has more ritual than any other religion, yet its canonical texts do not contain any rite for conversion. No better proof is needed for the fact that we have at no time either encouraged conversion or practiced it.
When a passenger arrives at a station by train he is besieged by the driver of the horse-cart, by the rikshavala, by the cabbie, and so on. He hires the vehicle in which he likes to be driven to his destination. It cannot be said with reason that those who ply different vehicles are guilty of competing with one another for the fare. After all it is their livelihood. But it makes no sense for the adherents of various faiths to vie with one another to take a man to the one and only destination that is God.
There is a bridge across a river, consisting of a number of arches, each of them built to the same design and measurement. To the man sitting next to a particular arch it would appear to be bigger than the other arches. So is the case with people belonging to a particular religion. They feel that their religion alone is great and want others to join it. There is in fact no such need for anyone to leave the religion of his birth for another.
That the beliefs and customs of the various religions are different cannot be a cause for complaint. Nor is there any need to make all of them similar. The important thing is for the followers of the various faiths to live in harmony with one another. The goal must be unity, not uniformity.
For a general background, please see here