No thief will enter heaven because, flesh and blood will not enter. In the twinkling of an eye we will be changed into perfect spirits. Its our new spirit that does not sin that will enter heaven. Our sinful flesh will not enter. So Paul is correct that those doing badness will not enter. Perhaps that is what Paul means.
1 Corinthians 15:50-58 King James Version (KJV)
50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
51 Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,
52 In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
53 For this corruptible must put on incorruption, and this mortal must put on immortality.
54 So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
55 O death, where is thy sting? O grave, where is thy victory?
56 The sting of death is sin; and the strength of sin is the law.
57 But thanks be to God, which giveth us the victory through our Lord Jesus Christ.
58 Therefore, my beloved brethren, be ye stedfast, unmoveable, always abounding in the work of the Lord, forasmuch as ye know that your labour is not in vain in the Lord.
King James Version (KJV)
Does that make sense Jackson? But note verse 58 which makes the point again about bearing good fruits because it says our labour is not in vain.