My straight forward answer is no.
And here is my reasoning why.
Firstly the name is Petition of Concern (PoC). So ask yourself "is one community adversely affected by the legislation that is proposed?". The answer is yes, in that the "conscience clause" is a bill that is only being appended to the Sexual Orientation Regulations of the Equality Act and only allowing people with a religion objection to refuse, without legal comeback, goods, facilities and services by that group on the basis of behaviour or belief. Therefore yes there is a concern that one part of society is being treated as inferior by a master society, this is a genuine concern.
It is not a Bill giving everyone the freedom to exercise their conscience, for in the DUP's eyes that would lead to MSM giving blood, Lesbian and Gay couples adopting, getting married, women having abortions and yeah also being allowed to refuse service to bigots who have been spotted outside their shop with anti-gay literature and then seeking to buy something from an shopkeeper who is LGBT or whose relative or friend is.
There is also the fact that once one group of people is allowed to use their individual conscience to refuse to serve others what other groups will argue they should have the same individual freedom. If we all had our individual freedoms honoured all the time there would be no collective responsibility and anarchy would rule.
But then we are Northern Ireland so it would have to be an even greater anarchy that we seem to have experienced.
Now of course the community affected immediately is not divided easily into "us uns" and "them uns" on the strict basis that the petition of concern was originally set up. There are LGBT people in both the protestant and catholic communities as well as in other faith groups and of no faith. There are LGBT people who recognise as Unionist, Nationalist or Other in the terms laid out for a vote in Stormont. Just as those in the other group are deemed to not have a valid opinion when any petition of concern is launched so it is that there is a flaw in the system. However, those who recognise as other are allowed to sign a PoC
Now the original questioner seems to see nothing wrong with blocking "same sex marriage" with a petition of concern. This is despite the fact that people in Northern Ireland have had civil partnerships in other parts of the UK which they can now convert to marriages, or have or are planning to have a same-sex marriage carries out elsewhere in the UK. These are not recognised as such here.
Another factor about the legislation on equal marriage that has been debated three times before Stormont is that each time it came before the floor of the chamber it had a built in conscience clause for all faith groups to make their own decision on whether they wanted to carry out same-sex marriages or not. The assumption may be that all faith groups here are opposed to the idea, that is not true. The petition of concern against opening up civil marriage to same sex couples and faith groups to have the option is a petition against people's freedom from religion as well as some faith groups freedom of religion.
Some people of faith have a conscience that allows them to marry people of the same-sex. Their conscience was actually denied by so called people of faith, speaking for all faith groups. Despite what the DUP say some people will use the conscience clause as a get out of jail free card when it comes to discrimination. I doubt that the questioner has ever experienced the looks and stares from Northern Irish business owners when you are in their establishment with a same-sex partner. I am not saying being overtly flirtatious, kissing or for that matter holding hands but clearly in a relationship and intimate through eye contact, words etc.
Currently the Equality Act means that under such circumstances protects all consumers from being refused. There is an issue with how certain messaging is handled, it is a grey area, something that can only be determined by case law, not by changing the law. I've heard the argument that same-sex marriage is illegal in Northern Ireland so they were right to refuse it.
However, it is not illegal to be a married same-sex couple in Northern Ireland, you are just re-labeled as civil partners. Also if the argument is that that no group can campaign on anything in the law being changed there would be no such thing as lobbying, indeed the camp at Twaddell Avenue set up to protest the legal decision made by the parades commission would also be something that nobody should campaign about under that logic of legality.
Having said that I don't like the petition of concern process. But while the DUP use it to block progress, on LGBT issues or integrated education or something else that doesn't appeal to their core. When it is being used to ensure that everyone is equal in the eyes of the law I think that is the correct usage. The shame of course is that the process has been abused too much by those on both sides that we fail to see it as serving a purpose to protect equality of opportunity (at least if you identify as Unionist or Nationalist).