Bismillah.
This is a very famously debated question. The concern here is that Maulid is bid’ah. Now, I am not a fan of controversial debates which divide the Ummah. And I am sure anyone can easily find the 2 different views and their elaboration in many religious sites. But since it is being asked, I’ll answer it.
According to Islamic scholars including Imam Nawawi, there are 2 types of Bid’ah: Hasanah & Saiyiah. Click here to read about it.
By “celebration of Maulid” I believe you are talking about commemorating the birth of best of mankind, our Prophet. Click here to read why and how Maulid is celebrated in general. :)
Basically, Maulid events occur with the purpose to remind and reiterate the Prophet’s journey and sacrifices to uphold and spread the religion. This would, insyallah, instill a deeper appreciation and affection for Rasul hence strengthening Iman. Something which strengthens the faith, is it against the teaching of Islam? It is really up to individuals to judge.
Whatever it is, differences in opinion should not be a factor which divides us Muslims. What we need now, more than ever, is unity. Instead of looking at differences, we should focus more on the core similarities - We bear witness that there is no god besides Allah, and Rasulullah is his messenger. We are bonded strong by this sincere faith of ours!
Yes, it is important to discuss about the differences, because we dont want others to be doing the wrong things. Despite so, at the end of the day, if we fail to agree on everything, do not let this minor differences in opinion be the reason we distant ourselves from each other. Learn to respect opposing views and love each other because of his or her faith for Allah.
One reason why Islam is not prevailing positively currently is because we are too busy fighting among ourselves. Just look at some Islamic countries, today. :( Imagine how strong (economically, socially etc.) we could be if all of us are united!
No, I am not digressing. I just hope, in the future, we could avoid controversial and potentially-dividing questions? At least in this page. Because, we are here to be united, despite our different backgrounds and opinions. Lillahita’ala.
Lastly. Please know that we love all of you members of MTS, for the sake of Allah. :)
Wallahua’lam.