Imagine a nation of 100 million wage-earners where each person earns $100,000 per year. The federal government is run frugally on an annual budget of $1 trillion dollars so that each wage-earner pays a tax of $10,000 per year - a 10% tax rate (as long as we're imagining, we might imagine something good). Everything thus far is obviously completely fair. As long as the government services provided are available to everyone, this could be argued to be a non-socialist system (I would still call it socialist because we have non-voluntary pooling of money for the greater good, but that's another argument).
Let us further imagine that half of the people own their homes, and the other half rents. To make our thought-problem simple, imagine that all the homes are exactly identical and all the mortgages are exactly identical, such that each owner pays $10,000 per year in interest.
Now into this utterly fair (but bland) world, we imagine the government deciding to institute a mortgage interest deduction to encourage home buying. Similar to present US rules, those that pay interest on their mortgages will be able to deduct this from their taxes. So the homeowners will now have an adjusted gross income of $90,000 per year, and will only pay taxes of $9000 per year. Since half the wage-earners owned homes, the result will be the federal government comes of $50 billion dollars short in its annual budget. So either the government has to run a deficit, which transfers wealth from future generations to the present generation, or tax rates must be raised. To balance the budget, the tax rate would be raised to 10.53%, then the renters will pay $10,527 in taxes and homeowners would pay $9,473 - a transfer of wealth from renters to owners.
Any way that you look at it, the home mortgage deduction is a transfer of wealth: either from the present renters, or from future generations. "Transfer of wealth" from one individual to another is inherently socialist.
Similar arguments can be made for any government program that benefits one group of persons in a way that isn't available to all. All tax breaks are inherently socialist - someone has to pick up the slack. So if one person pays less, another must pay more.
So, if you gladly take the home mortgage interest deduction (or the child care deduction, etc.), let us not hear blanket condemnation for all socialism, which would be fundamentally hypocritical. If you honestly abhor socialism (rather than just disliking the transfer of your wealth to someone else), then make sure you don't take that mortgage deduction next year so that you can pay for your fair share of the government. Even if you don't like all the government's programs, if you are consistent and have true beliefs that socialism is wrong then you will pay for your fair share rather than foist it on someone else. Every dollar you take in a deduction is a dollar that someone who doesn't have the deduction will have to pay. You are taking their wealth. If you take the deduction, you are enjoying the fruits of someone else's labor - you've bitten the socialist apple and know its taste - let's see you spit it out rather than benefit from the nutrition.