It parallels the workplace issue of will you give a job to someone with a criminal record. A lot of people say they feel they can't be sure of the person. Others say it depends on the individual cirumstances.
In the situation you gave, the main point is whether the operative word is _past_. Have they since left the gang into which they entered through circumstance or overriding local culture; have they left behind the negative aspects it brought into their life, and now (and for the future) adamantly want to uphold the ideals of your organisation? !
I realise I haven't given my answer to your closed question yet.
eta: might fix the grammar later
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