I'll answer you in english since I don't speak spanish. By the way if you want to know what most of the people think about this, try to create a topic in the section named "RC Lens" (the first).
I think there are 2 types of reactions about your club investing in ours.
Thirst there are people who are against. They think the RC Lens should'nt be affiliated (as the "underling") to any other because Lens belong to the best clubs of our country and is soon destinated to reach european competition again. So this basicaly isn't against Atletico but would be wih any other club.
And there are people who accept this situation. We recently had serious economic problems with our last owner (Hafiz Mamadov from Azerbaidjan, one of the man involved in your "Land of Fire" too i guess) and were close to bankrupt. So having someone wo can provide money consistently is a good thing.
The fact that this someone is/belong to your club make them hope we'll benefit of your knowledge in all aspect (economic, recruitment network etc.) and from this point of view being affiliated to a top club like Atletico only make things better.
As for me I see your club like i would do with any other investor. The RC Lens is a good opportunity to make profit if they manage to put the club in L1 again and improve his finance and they'll certainly sell it as soon as they achieve these objectives. The difference from a common investor is that we can benefit from your knowledge as a fellow and successfull football club so it may be really profitable for us (and maybe for you if one of our youngs players turn out to be the next Aurier, Kondogbia or Varane).
By the way, do you think there are players in your second team who could to come here on loan ?
I used to think spanish teams from La Liga mostly grant their loans to other spanish teams but maybe am I wrong ?