"Allah will bring a people whom He will love, and they love Him!"

“Allah will bring a people whom He will love, and they love Him…” [5:54]

This is a follow up to the conditional clause that precedes, wherein He says:

"O you who believe, whoever from among you turns back from deen, Allah will bring a people whom He will love and they will love Him"

That is, if you turn back from the Deen of Allah, that will not harm Allah in any way:

"Allah will bring a people whom He will love, and they love Him…" [5:54]

This is like His statement:

"And if you turn away, He will exchange you for some other people, and they will not be your likes." [47:38]

Whoever turns back from the Deen of Allah, Allah is not concerned, because He has no need of him. Rather, He will eliminate them, and bring one who is better than him.

"Allah will soon bring" Instead of them:

"He will love them and they will love Him"

If they Allah, and He loves them, they will abide in His obedience. The completion of the Ayah:

"Humble towards the believers, stern towards the disbelievers." [5:54]

They are humble before the believers, they lower their wings and are lenient with the believers, and they are peaceful with each other. But to the disbelievers, they are stern and strong. They never exhibit submissiveness before the disbelievers. 
 

The Messenger (saws) taught us that, “If you meet them (need and christians) on a path, constrain them to the narrowest part of it.” [Muslim]. If the jews and christians meet you, even if they are a thousand and you are just ten, we will make things difficult for this group. We will not give way to them, we will rather force them to the narrows. We will show them the might of this Deen, not ourselves because we are human beings and they are human beings, such that it becomes clear to them that the Deen of Islam is dominant, and he who adheres to it is the mighty one.

"Struggling for the sake of Allah and never fearing the blame of the blamers." [5:54]

They perform struggle for the sake of Allah, everyone who opposes the Deen of Allah among the disbelievers, the rebellious, the herectics, and the apostates. They fight everyone with the weapons they deserve. Whoever fights them with iron and fire, they fight them with iron and fire. Whoever fights them with debate and arguments, they argue with him with the like of that. They struggle for Allah.

"And never fearing the blame of the blamers"

They do  it fear the blame of the people. They speak the truth, even if it is against themselves. But they employ wisdom in this Struggle, and they aspire to achieve the goal. If they see that the Da’wah demands some delay in some matters, they delay. If they see that doing Da’wah demands leniency in some situations, they use it because they want to reach a particular goal, and the means are according to what the situation demands. Then Allah says:

"That is the grace of Allah which He bestows on whom He wills and Allah is All Sufficient for His creations’ needs, All Knower." [5:54]

[Sharh ‘Aqeedatul Wasatiyyah, By Shaykh Muhammad ibnu Salih Al ‘Uthaymeen]