The -ㄹ ending of a verb represents a potential or hypothetical case, i.e. something which might happen (usually conflicting with normal expectation or wish), and the future tense comes from this sense. It is similar to the to-infinitive in English which can represnent what might happen. So it's good to keep in mind that it doess not always express the future time.
For example, these phrases show something waiting to happen rather than in the future.
- 할 일 = things to do.
- 갈 시간이 됐다 = It is time to go.
~(으)ㄹ지라도 thus expresses a possible conflicting situation, such as you might not have thought would bring about the results mentioned in the main clause, similar to the subjunctive mood in English. There are other similar consturcts without the -ㄹ and which are weaker in the sense of subjunctivity.
So, compare these.
1. 평신도라고 할 지라도 = 평신도랄지라도 = even if they (should) happen to be a layperson.
2. 평신도라고 하더라도 = 평신도라더라도 = even if they are a layperson (sounds less subjunctive, more ordinary).
3. 평신도라고 해도 = 평신도래도 = no matter that they are a layperson (almost no subjunctive implication).
Your sentence has the subject omitted. The subject might be the written text itself or the person who wrote it.
- (이것은/그것은/나는/그는...) 독자가 신학에 관한 지식이 없는 평신도라고 할지라도 교회 교육에 관심을 두고 있는 사람이라면 꼭 알아야 될 기본적인 것들을 기독교 교육학적인 측면에서 적은 것이다.
=> It is a piece written from an educational perspective about the basic things that any reader concerned with the Christian education should know, even if they happen to be a layperson with little knowledge about theology.